Merge lp:~barry/ubuntu-system-image/citrain-2.1 into lp:~ubuntu-managed-branches/ubuntu-system-image/system-image

[Barry Warsaw]

New upstream release, along with some packaging changes. See changelog and NEWS.rst for details.

  [ Stéphane Graber ]
  * New upstream release.
  * Set X-Auto-Uploader to no-rewrite-version
  * Set Vcs-Bzr to the new target branch

  [ Barry Warsaw ]
  * New upstream release.
    - LP: #1279056 - Internal improvements to SignatureError for
      better debugging.
    - LP: #1277589 - Better protection against race conditions.
    - LP: #1260768 - Return empty string from ApplyUpdate D-Bus method.
    - Request ubuntu-download-manager to download to a temporary location,
      with atomic rename.
    - More detailed logging.
    - Fixed D-Bus error logging.
    - Added -L flag to nose2 tests for explicitly setting log file path.
    - Added SYSTEMIMAGE_DBUS_DAEMON_HUP_SLEEP_SECONDS environment variable
      which can be used to give virtualized buildds a fighting chance.
  * d/patches/01_send_ack_on_applyupdate.diff - Removed; applied upstream.
  * d/control: Bump Standards-Version to 3.9.5 with no other changes necessary.

[lp:~barry/ubuntu-system-image/citrain-2.1]

234. By Barry Warsaw on 2014-02-24

* d/control:
  - Bump Standards-Version to 3.9.5 with no other changes necessary.
  - Add python3-psutil as Depends to system-image-dev.

235. By Barry Warsaw on 2014-02-25

d/rules: Set SYSTEMIMAGE_DBUS_DAEMON_HUP_SLEEP_SECONDS to 1 to deal with
buildd dbus-daemon SIGHUP timing issues.

236. By Barry Warsaw on 2014-02-25

  - LP: #1284217 - Send UpdateAvailableStatus during auto-downloading
    from a previous CheckForUpdate, if cached status is available.
* d/patches/01_send_ack_on_applyupdate.diff: Removed; applied upstream.
* d/patches/lp1284217.patch: Added (see above).

237. By Barry Warsaw on 2014-02-25

Update patch

=== modified file 'MANIFEST.in'
--- MANIFEST.in	2013-12-13 13:55:51 +0000
+++ MANIFEST.in	2014-02-25 17:45:25 +0000
@@ -3,4 +3,5 @@
 prune build
 prune dist
 prune .tox
+prune .bzr
 exclude .bzrignore

=== modified file 'NEWS.rst'
--- NEWS.rst	2013-12-13 13:55:51 +0000
+++ NEWS.rst	2014-02-25 17:45:25 +0000
@@ -2,7 +2,54 @@
 NEWS for system-image updater
 =============================
 
-2.0.3 (2013-XX-XX)
+2.1 (2014-02-20)
+================
+ * Internal improvements to SignatureError for better debugging. (LP: #1279056)
+ * Better protection against several possible race conditions during
+   `CheckForUpdate()` (LP: #1277589)
+   - Use a threading.Lock instance as the internal "checking for update"
+     barrier instead of a boolean.  This should eliminate the race window
+     between testing and acquiring the checking lock.
+   - Put an exclusive claim on the `com.canonical.SystemImage` system dbus
+     name, and if we cannot get that claim, exit with an error code 2.  This
+     prevents multiple instances of the D-Bus system service from running at
+     the same time.
+ * Return the empty string from `ApplyUpdate()` D-Bus method.  This restores
+   the original API (patch merged from Ubuntu package, given by Didier
+   Roche).  (LP: #1260768)
+ * Request ubuntu-download-manager to download all files to temporary
+   destinations, then atomically rename them into place.  This avoids
+   clobbering by multiple processes and mimics changes coming in u-d-m.
+ * Provide much more detailed logging.
+   - `Mediator` instances have a helpful `repr` which also includes the id of
+     the `State` object.
+   - More logging during state transitions.
+   - All emitted D-Bus signals are also logged (at debug level).
+ * Added `-L` flag to nose test runner, which can be used to specify an
+   explicit log file path for debugging.
+ * Fixed D-Bus error logging.
+   - Don't initialize the root logger, since this can interfere with
+     python-dbus, which doesn't initialize its loggers correctly.
+   - Only use `.format()` based interpolation for `systemimage` logs.
+ * Give virtualized buildds a fighting chance against D-Bus by
+   - using `org.freedesktop.DBus`s `ReloadConfig()` interface instead of
+     SIGHUP.
+   - add a configurable sleep call after the `ReloadConfig()`.  This defaults
+     to 0 since de-virtualized and local builds do not need them.  Set the
+     environment variable `SYSTEMIMAGE_DBUS_DAEMON_HUP_SLEEP_SECONDS` to
+     override.
+  * Run the tox test suite for both Python 3.3 and 3.4.
+
+2.0.5 (2014-01-30)
+==================
+ * MANIFEST.in: Make sure the .bzr directory doesn't end up in the
+   sdist tarball.
+
+2.0.4 (2014-01-30)
+==================
+ * No change release to test the new landing process.
+
+2.0.3 (2013-12-11)
 ==================
  * More attempted DEP-8 test failure fixes.
 

=== modified file 'PKG-INFO'
--- PKG-INFO	2013-12-13 13:55:51 +0000
+++ PKG-INFO	2014-02-25 17:45:25 +0000
@@ -1,6 +1,6 @@
 Metadata-Version: 1.0
 Name: system-image
-Version: 2.0.3
+Version: 2.1
 Summary: Ubuntu System Image Based Upgrades
 Home-page: UNKNOWN
 Author: Barry Warsaw

=== modified file 'cli-manpage.rst'
--- cli-manpage.rst	2013-12-13 13:55:51 +0000
+++ cli-manpage.rst	2014-02-25 17:45:25 +0000
@@ -8,7 +8,7 @@
 
 :Author: Barry Warsaw <[e-mail]>
 :Date: 2013-10-23
-:Copyright: 2013 Canonical Ltd.
+:Copyright: 2013-2014 Canonical Ltd.
 :Version: 2.0
 :Manual section: 1
 

=== modified file 'dbus-manpage.rst'
--- dbus-manpage.rst	2013-12-13 13:55:51 +0000
+++ dbus-manpage.rst	2014-02-25 17:45:25 +0000
@@ -8,7 +8,7 @@
 
 :Author: Barry Warsaw <[e-mail]>
 :Date: 2013-07-31
-:Copyright: 2013 Canonical Ltd.
+:Copyright: 2013-2014 Canonical Ltd.
 :Version: 1.0
 :Manual section: 8
 

=== modified file 'debian/changelog'
--- debian/changelog	2013-12-13 13:55:51 +0000
+++ debian/changelog	2014-02-25 17:45:25 +0000
@@ -1,3 +1,35 @@
+system-image (2.1-0ubuntu4) UNRELEASED; urgency=medium
+
+  [ Stéphane Graber ]
+  * New upstream release.
+  * Set X-Auto-Uploader to no-rewrite-version
+  * Set Vcs-Bzr to the new target branch
+
+  [ Barry Warsaw ]
+  * New upstream release.
+    - LP: #1279056 - Internal improvements to SignatureError for
+      better debugging.
+    - LP: #1277589 - Better protection against race conditions.
+    - LP: #1260768 - Return empty string from ApplyUpdate D-Bus method.
+    - LP: #1284217 - Send UpdateAvailableStatus during auto-downloading
+      from a previous CheckForUpdate, if cached status is available.
+    - Request ubuntu-download-manager to download to a temporary location,
+      with atomic rename.
+    - More detailed logging.
+    - Fixed D-Bus error logging.
+    - Added -L flag to nose2 tests for explicitly setting log file path.
+    - Added SYSTEMIMAGE_DBUS_DAEMON_HUP_SLEEP_SECONDS environment variable
+      which can be used to give virtualized buildds a fighting chance.
+  * d/patches/01_send_ack_on_applyupdate.diff: Removed; applied upstream.
+  * d/patches/lp1284217.patch: Added (see above).
+  * d/control:
+    - Bump Standards-Version to 3.9.5 with no other changes necessary.
+    - Add python3-psutil as Depends to system-image-dev.
+  * d/rules: Set SYSTEMIMAGE_DBUS_DAEMON_HUP_SLEEP_SECONDS to 1 to deal with
+    buildd dbus-daemon SIGHUP timing issues.
+
+ -- Barry Warsaw <[e-mail]>  Thu, 20 Feb 2014 18:03:10 -0500
+
 system-image (2.0.3-0ubuntu2) trusty; urgency=low
 
   * Fix ApplyUpdate() to return an empty string as per spec if the update

=== modified file 'debian/control'
--- debian/control	2013-12-13 13:55:51 +0000
+++ debian/control	2014-02-25 17:45:25 +0000
@@ -18,10 +18,11 @@
                python3-psutil,
                python3-setuptools,
                ubuntu-download-manager
-Standards-Version: 3.9.4
+Standards-Version: 3.9.5
 XS-Testsuite: autopkgtest
-Vcs-Bzr: https://code.launchpad.net/~ubuntu-system-image/ubuntu-system-image/client.pkg
-Vcs-Browser: http://bazaar.launchpad.net/~ubuntu-system-image/ubuntu-system-image/client.pkg/files
+Vcs-Bzr: https://code.launchpad.net/~ubuntu-managed-branches/ubuntu-system-image/system-image
+Vcs-Browser: http://bazaar.launchpad.net/~ubuntu-managed-branches/ubuntu-system-image/system-image/files
+X-Auto-Uploader: no-rewrite-version
 
 Package: system-image-cli
 Architecture: all
@@ -53,7 +54,7 @@
 
 Package: system-image-dev
 Architecture: all
-Depends: python3-gnupg, ${misc:Depends}, ${python3:Depends}
+Depends: python3-gnupg, python3-psutil, ${misc:Depends}, ${python3:Depends}
 Description: Ubuntu system image updater development
  This is the development bits for the Ubuntu system image updater.
  Install this package if you want to run the tests.

=== removed file 'debian/patches/01_send_ack_on_applyupdate.diff'
--- debian/patches/01_send_ack_on_applyupdate.diff	2013-12-13 13:55:51 +0000
+++ debian/patches/01_send_ack_on_applyupdate.diff	1970-01-01 00:00:00 +0000
@@ -1,16 +0,0 @@
-Description: Send ack on apply diff
- Fix ApplyUpdate() to return an empty string as per spec if the update
- is successfull (LP: #1260712)
-Author: Didier Roche <[e-mail]>
-Bug-Ubuntu: https://bugs.launchpad.net/bugs/1260712
-
---- system-image-2.0.3.orig/systemimage/dbus.py
-+++ system-image-2.0.3/systemimage/dbus.py
-@@ -233,6 +233,7 @@ class Service(Object):
-     def ApplyUpdate(self):
-         """Apply the update, rebooting the device."""
-         GLib.timeout_add(50, self._apply_update)
-+        return ""
- 
-     @method('com.canonical.SystemImage', out_signature='isssa{ss}')
-     def Info(self):

=== added file 'debian/patches/lp1284217.patch'
--- debian/patches/lp1284217.patch	1970-01-01 00:00:00 +0000
+++ debian/patches/lp1284217.patch	2014-02-25 17:45:25 +0000
@@ -0,0 +1,106 @@
+Description: Backport of fix for LP: #1284217.  This adds an additional
+  UpdateAvailableStatus signal when a second CheckForUpdate is called while an
+  auto-download is in progress, but only if we have cached status available.
+Origin: http://bazaar.launchpad.net/~ubuntu-system-image/ubuntu-system-image/client/revision/240?start_revid=240
+Bug: http://pad.lv/1284217
+Forwarded: not-needed
+
+=== modified file 'systemimage/dbus.py'
+--- old/systemimage/dbus.py	2014-02-18 22:31:55 +0000
++++ new/systemimage/dbus.py	2014-02-25 17:27:14 +0000
+@@ -131,7 +131,20 @@
+         # Check-and-acquire the lock.
+         log.info('test and acquire checking lock')
+         if not self._checking.acquire(blocking=False):
+-            # Check is already in progress, so there's nothing more to do.
++            # Check is already in progress, so there's nothing more to do.  If
++            # there's status available (i.e. we are in the auto-downloading
++            # phase of the last CFU), then send the status.
++            if self._update is not None:
++                self.UpdateAvailableStatus(
++                    self._update.is_available,
++                    self._downloading,
++                    self._update.version,
++                    self._update.size,
++                    self._update.last_update_date,
++                    # XXX 2013-08-22 - the u/i cannot currently currently
++                    # handle the array of dictionaries data type.  LP:
++                    # #1215586 self._update.descriptions,
++                    "")
+             log.info('checking lock not acquired')
+             return
+         log.info('checking lock acquired')
+
+=== modified file 'systemimage/tests/test_dbus.py'
+--- old/systemimage/tests/test_dbus.py	2014-02-18 20:02:59 +0000
++++ new/systemimage/tests/test_dbus.py	2014-02-25 17:27:14 +0000
+@@ -23,13 +23,13 @@
+     'TestDBusGetSet',
+     'TestDBusInfo',
+     'TestDBusInfoNoDetails',
+-    'TestDBusLP1277589',
+     'TestDBusMockFailApply',
+     'TestDBusMockFailPause',
+     'TestDBusMockFailResume',
+     'TestDBusMockNoUpdate',
+     'TestDBusMockUpdateAutoSuccess',
+     'TestDBusMockUpdateManualSuccess',
++    'TestDBusMultipleChecksInFlight',
+     'TestDBusPauseResume',
+     'TestDBusProgress',
+     'TestDBusRegressions',
+@@ -133,6 +133,7 @@
+         self.schedule(self.iface.CheckForUpdate)
+ 
+     def _do_UpdateAvailableStatus(self, signal, path, *args, **kws):
++        # We'll keep doing this until we get the UpdateDownloaded signal.
+         self.uas_signals.append(args)
+         self.schedule(self.iface.CheckForUpdate)
+ 
+@@ -1563,7 +1564,7 @@
+ """)
+ 
+ 
+-class TestDBusLP1277589(_LiveTesting):
++class TestDBusMultipleChecksInFlight(_LiveTesting):
+     def test_multiple_check_for_updates(self):
+         # Log analysis of LP: #1277589 appears to show the following scenario,
+         # reproduced in this test case:
+@@ -1588,18 +1589,23 @@
+         # signal, we'll immediately issue *another* CheckForUpdate, which
+         # should run while the auto-download is working.
+         #
+-        # At the end, we should not get another UpdateAvailableStatus signal,
+-        # but we should get the UpdateDownloaded signal.
++        # As per LP: #1284217, we will get a second UpdateAvailableStatus
++        # signal, since the status is available even while the original
++        # request is being downloaded.
+         reactor = DoubleCheckingReactor(self.iface)
+         reactor.run()
+-        self.assertEqual(len(reactor.uas_signals), 1)
+-        (is_available, downloading, available_version, update_size,
+-         last_update_date,
+-         #descriptions,
+-         error_reason) = reactor.uas_signals[0]
+-        self.assertTrue(is_available)
+-        self.assertTrue(downloading)
+-        self.assertEqual(available_version, '1600')
+-        self.assertEqual(update_size, 314572800)
+-        self.assertEqual(last_update_date, 'Unknown')
+-        self.assertEqual(error_reason, '')
++        # We need to have received at least 2 signals, but due to timing
++        # issues it could possibly be more.
++        self.assertGreater(len(reactor.uas_signals), 1)
++        # All received signals should have the same information.
++        for signal in reactor.uas_signals:
++            (is_available, downloading, available_version, update_size,
++             last_update_date,
++             #descriptions,
++             error_reason) = signal
++            self.assertTrue(is_available)
++            self.assertTrue(downloading)
++            self.assertEqual(available_version, '1600')
++            self.assertEqual(update_size, 314572800)
++            self.assertEqual(last_update_date, 'Unknown')
++            self.assertEqual(error_reason, '')
+

=== modified file 'debian/patches/series'
--- debian/patches/series	2013-12-13 13:55:51 +0000
+++ debian/patches/series	2014-02-25 17:45:25 +0000
@@ -1,1 +1,1 @@
-01_send_ack_on_applyupdate.diff
+lp1284217.patch

=== modified file 'debian/rules'
--- debian/rules	2013-12-13 13:55:51 +0000
+++ debian/rules	2014-02-25 17:45:25 +0000
@@ -16,6 +16,7 @@
 test-python%:
 	unset http_proxy; unset https_proxy; export HOME=/tmp; \
 	export SYSTEMIMAGE_REACTOR_TIMEOUT=1200; \
+	export SYSTEMIMAGE_DBUS_DAEMON_HUP_SLEEP_SECONDS=2; \
 	nodot=$(shell echo $* | cut --complement -b 2); \
 	tox -e py$${nodot}
 

=== modified file 'ini-manpage.rst'
--- ini-manpage.rst	2013-12-13 13:55:51 +0000
+++ ini-manpage.rst	2014-02-25 17:45:25 +0000
@@ -9,7 +9,7 @@
 
 :Author: Barry Warsaw <[e-mail]>
 :Date: 2013-10-11
-:Copyright: 2013 Canonical Ltd.
+:Copyright: 2013-2014 Canonical Ltd.
 :Version: 1.9
 :Manual section: 5
 

=== modified file 'setup.cfg'
--- setup.cfg	2013-12-13 13:55:51 +0000
+++ setup.cfg	2014-02-25 17:45:25 +0000
@@ -4,7 +4,7 @@
 logging-filter = systemimage
 
 [egg_info]
+tag_svn_revision = 0
+tag_date = 0
 tag_build = 
-tag_date = 0
-tag_svn_revision = 0
 

=== modified file 'setup.py'
--- setup.py	2013-12-13 13:55:51 +0000
+++ setup.py	2014-02-25 17:45:25 +0000
@@ -1,4 +1,4 @@
-# Copyright (C) 2013 Canonical Ltd.
+# Copyright (C) 2013-2014 Canonical Ltd.
 # Author: Barry Warsaw <[e-mail]>
 
 # This program is free software: you can redistribute it and/or modify

=== modified file 'system_image.egg-info/PKG-INFO'
--- system_image.egg-info/PKG-INFO	2013-12-13 13:55:51 +0000
+++ system_image.egg-info/PKG-INFO	2014-02-25 17:45:25 +0000
@@ -1,6 +1,6 @@
 Metadata-Version: 1.0
 Name: system-image
-Version: 2.0.3
+Version: 2.1
 Summary: Ubuntu System Image Based Upgrades
 Home-page: UNKNOWN
 Author: Barry Warsaw

=== modified file 'system_image.egg-info/SOURCES.txt'
--- system_image.egg-info/SOURCES.txt	2013-12-13 13:55:51 +0000
+++ system_image.egg-info/SOURCES.txt	2014-02-25 17:45:25 +0000
@@ -7,7 +7,6 @@
 setup.py
 tox.ini
 unittest.cfg
-.bzr/branch/branch.conf
 system_image.egg-info/PKG-INFO
 system_image.egg-info/SOURCES.txt
 system_image.egg-info/dependency_links.txt
@@ -126,6 +125,7 @@
 systemimage/tests/data/index_21.json
 systemimage/tests/data/index_22.json
 systemimage/tests/data/index_23.json
+systemimage/tests/data/index_24.json
 systemimage/tests/data/key.pem
 systemimage/tests/data/master-secring.gpg
 systemimage/tests/data/nasty_cert.pem

=== modified file 'systemimage/api.py'
--- systemimage/api.py	2013-12-13 13:55:51 +0000
+++ systemimage/api.py	2014-02-25 17:45:25 +0000
@@ -1,4 +1,4 @@
-# Copyright (C) 2013 Canonical Ltd.
+# Copyright (C) 2013-2014 Canonical Ltd.
 # Author: Barry Warsaw <[e-mail]>
 
 # This program is free software: you can redistribute it and/or modify
@@ -73,6 +73,10 @@
         self._update = None
         self._callback = callback
 
+    def __repr__(self):
+        return '<Mediator at 0x{:x} | State at 0x{:x}>'.format(
+            id(self), id(self._state))
+
     def cancel(self):
         self._state.downloader.cancel()
 

=== modified file 'systemimage/bag.py'
--- systemimage/bag.py	2013-12-13 13:55:51 +0000
+++ systemimage/bag.py	2014-02-25 17:45:25 +0000
@@ -1,4 +1,4 @@
-# Copyright (C) 2013 Canonical Ltd.
+# Copyright (C) 2013-2014 Canonical Ltd.
 # Author: Barry Warsaw <[e-mail]>
 
 # This program is free software: you can redistribute it and/or modify

=== modified file 'systemimage/bindings.py'
--- systemimage/bindings.py	2013-12-13 13:55:51 +0000
+++ systemimage/bindings.py	2014-02-25 17:45:25 +0000
@@ -1,4 +1,4 @@
-# Copyright (C) 2013 Canonical Ltd.
+# Copyright (C) 2013-2014 Canonical Ltd.
 # Author: Barry Warsaw <[e-mail]>
 
 # This program is free software: you can redistribute it and/or modify

=== modified file 'systemimage/candidates.py'
--- systemimage/candidates.py	2013-12-13 13:55:51 +0000
+++ systemimage/candidates.py	2014-02-25 17:45:25 +0000
@@ -1,4 +1,4 @@
-# Copyright (C) 2013 Canonical Ltd.
+# Copyright (C) 2013-2014 Canonical Ltd.
 # Author: Barry Warsaw <[e-mail]>
 
 # This program is free software: you can redistribute it and/or modify

=== modified file 'systemimage/channel.py'
--- systemimage/channel.py	2013-12-13 13:55:51 +0000
+++ systemimage/channel.py	2014-02-25 17:45:25 +0000
@@ -1,4 +1,4 @@
-# Copyright (C) 2013 Canonical Ltd.
+# Copyright (C) 2013-2014 Canonical Ltd.
 # Author: Barry Warsaw <[e-mail]>
 
 # This program is free software: you can redistribute it and/or modify

=== modified file 'systemimage/config.py'
--- systemimage/config.py	2013-12-13 13:55:51 +0000
+++ systemimage/config.py	2014-02-25 17:45:25 +0000
@@ -1,4 +1,4 @@
-# Copyright (C) 2013 Canonical Ltd.
+# Copyright (C) 2013-2014 Canonical Ltd.
 # Author: Barry Warsaw <[e-mail]>
 
 # This program is free software: you can redistribute it and/or modify

=== modified file 'systemimage/dbus.py'
--- systemimage/dbus.py	2013-12-13 13:55:51 +0000
+++ systemimage/dbus.py	2014-02-25 17:45:25 +0000
@@ -1,4 +1,4 @@
-# Copyright (C) 2013 Canonical Ltd.
+# Copyright (C) 2013-2014 Canonical Ltd.
 # Author: Barry Warsaw <[e-mail]>
 
 # This program is free software: you can redistribute it and/or modify
@@ -23,6 +23,7 @@
 
 import os
 import sys
+import logging
 import traceback
 
 from dbus.service import Object, method, signal
@@ -31,9 +32,11 @@
 from systemimage.config import config
 from systemimage.helpers import last_update_date, version_detail
 from systemimage.settings import Settings
+from threading import Lock
 
 
 EMPTYSTRING = ''
+log = logging.getLogger('systemimage')
 
 
 class Loop:
@@ -68,7 +71,8 @@
         super().__init__(bus, object_path)
         self._loop = loop
         self._api = Mediator(self._progress_callback)
-        self._checking = False
+        log.info('Mediator created {}', self._api)
+        self._checking = Lock()
         self._update = None
         self._downloading = False
         self._paused = False
@@ -78,17 +82,22 @@
 
     def _check_for_update(self):
         # Asynchronous method call.
+        log.info('Checking for update')
         self._update = self._api.check_for_update()
         # Do we have an update and can we auto-download it?
         downloading = False
         if self._update.is_available:
             settings = Settings()
             auto = settings.get('auto_download')
+            log.info('Update available; auto-download: {}', auto)
             if auto in ('1', '2'):
                 # XXX When we have access to the download service, we can
                 # check if we're on the wifi (auto == '1').
-                GLib.timeout_add(50, self._download)
+                GLib.timeout_add(50, self._download, self._checking.release)
                 downloading = True
+            else:
+                log.info('release checking lock from _check_for_update()')
+                self._checking.release()
         self.UpdateAvailableStatus(
             self._update.is_available,
             downloading,
@@ -99,7 +108,6 @@
             # array of dictionaries data type.  LP: #1215586
             #self._update.descriptions,
             "")
-        self._checking = False
         # Stop GLib from calling this method again.
         return False
 
@@ -120,13 +128,17 @@
         whether the update is available or not.
         """
         self._loop.keepalive()
-        if self._checking:
+        # Check-and-acquire the lock.
+        log.info('test and acquire checking lock')
+        if not self._checking.acquire(blocking=False):
             # Check is already in progress, so there's nothing more to do.
+            log.info('checking lock not acquired')
             return
-        self._checking = True
-        # Reset any failure or in-progress state.  Get a new mediator to reset
-        # any of its state.
+        log.info('checking lock acquired')
+        # We've now acquired the lock.  Reset any failure or in-progress
+        # state.  Get a new mediator to reset any of its state.
         self._api = Mediator(self._progress_callback)
+        log.info('Mediator recreated {}', self._api)
         self._failure_count = 0
         self._last_error = ''
         # Arrange for the actual check to happen in a little while, so that
@@ -141,24 +153,28 @@
         eta = 0
         self.UpdateProgress(percentage, eta)
 
-    def _download(self):
+    def _download(self, release_checking=None):
         if self._downloading and self._paused:
             self._api.resume()
             self._paused = False
+            log.info('Download previously paused')
             return
-        if (self._downloading                        # Already in progress.
-            or self._update is None                  # Not yet checked.
-            or not self._update.is_available         # No update available.
+        if (self._downloading                           # Already in progress.
+            or self._update is None                     # Not yet checked.
+            or not self._update.is_available            # No update available.
             ):
+            log.info('Download already in progress or not available')
             return
         if self._failure_count > 0:
             self._failure_count += 1
             self.UpdateFailed(self._failure_count, self._last_error)
+            log.info('Update failure count: {}', self._failure_count)
             return
         self._downloading = True
+        log.info('Update is downloading')
         try:
-            # Always start by sending a UpdateProgress(0, 0).  This is enough
-            # to get the u/i's attention.
+            # Always start by sending a UpdateProgress(0, 0).  This is
+            # enough to get the u/i's attention.
             self.UpdateProgress(0, 0)
             self._api.download()
         except Exception:
@@ -167,13 +183,20 @@
             # value, but not the traceback.
             self._last_error = EMPTYSTRING.join(
                 traceback.format_exception_only(*sys.exc_info()[:2]))
+            log.info('Update failed: {}', self._last_error)
             self.UpdateFailed(self._failure_count, self._last_error)
         else:
+            log.info('Update downloaded')
             self.UpdateDownloaded()
             self._failure_count = 0
             self._last_error = ''
             self._rebootable = True
         self._downloading = False
+        log.info('release checking lock from _download()')
+        if release_checking is not None:
+            # We were auto-downloading, so we now have to release the checking
+            # lock.  If we were manually downloading, there would be no lock.
+            release_checking()
         # Stop GLib from calling this method again.
         return False
 
@@ -216,8 +239,6 @@
         return ''
 
     def _apply_update(self):
-        # This signal may or may not get sent.  We're racing against the
-        # system reboot procedure.
         self._loop.keepalive()
         if not self._rebootable:
             command_file = os.path.join(
@@ -227,12 +248,16 @@
                 self.Rebooting(False)
                 return
         self._api.reboot()
+        # This code may or may not run.  We're racing against the system
+        # reboot procedure.
+        self._rebootable = False
         self.Rebooting(True)
 
     @method('com.canonical.SystemImage')
     def ApplyUpdate(self):
         """Apply the update, rebooting the device."""
         GLib.timeout_add(50, self._apply_update)
+        return ''
 
     @method('com.canonical.SystemImage', out_signature='isssa{ss}')
     def Info(self):
@@ -294,31 +319,40 @@
                               #descriptions,
                               error_reason):
         """Signal sent in response to a CheckForUpdate()."""
+        log.debug('EMIT UpdateAvailableStatus({}, {}, {}, {}, {}, {})',
+                  is_available, downloading, available_version, update_size,
+                  last_update_date, repr(error_reason))
         self._loop.keepalive()
 
     @signal('com.canonical.SystemImage', signature='id')
     def UpdateProgress(self, percentage, eta):
         """Download progress."""
+        log.debug('EMIT UpdateProgress({}, {})', percentage, eta)
         self._loop.keepalive()
 
     @signal('com.canonical.SystemImage')
     def UpdateDownloaded(self):
         """The update has been successfully downloaded."""
+        log.debug('EMIT UpdateDownloaded()')
         self._loop.keepalive()
 
     @signal('com.canonical.SystemImage', signature='is')
     def UpdateFailed(self, consecutive_failure_count, last_reason):
         """The update failed for some reason."""
+        log.debug('EMIT UpdateFailed({}, {})',
+                  consecutive_failure_count, repr(last_reason))
         self._loop.keepalive()
 
     @signal('com.canonical.SystemImage', signature='i')
     def UpdatePaused(self, percentage):
         """The download got paused."""
+        log.debug('EMIT UpdatePaused({})', percentage)
         self._loop.keepalive()
 
     @signal('com.canonical.SystemImage', signature='ss')
     def SettingChanged(self, key, new_value):
         """A setting value has change."""
+        log.debug('EMIT SettingChanged({}, {})', repr(key), repr(new_value))
         self._loop.keepalive()
 
     @signal('com.canonical.SystemImage', signature='b')
@@ -326,3 +360,4 @@
         """The system is rebooting."""
         # We don't need to keep the loop alive since we're probably just going
         # to shutdown anyway.
+        log.debug('EMIT Rebooting({})', status)

=== modified file 'systemimage/device.py'
--- systemimage/device.py	2013-12-13 13:55:51 +0000
+++ systemimage/device.py	2014-02-25 17:45:25 +0000
@@ -1,4 +1,4 @@
-# Copyright (C) 2013 Canonical Ltd.
+# Copyright (C) 2013-2014 Canonical Ltd.
 # Author: Barry Warsaw <[e-mail]>
 
 # This program is free software: you can redistribute it and/or modify

=== modified file 'systemimage/docs/conf.py'
--- systemimage/docs/conf.py	2013-12-13 13:55:51 +0000
+++ systemimage/docs/conf.py	2014-02-25 17:45:25 +0000
@@ -41,7 +41,7 @@
 
 # General information about the project.
 project = u'Image Update Resolver'
-copyright = u'2013, Canonical Ltd.'
+copyright = u'2013-2014, Canonical Ltd.'
 
 # The version info for the project you're documenting, acts as replacement for
 # |version| and |release|, also used in various other places throughout the

=== modified file 'systemimage/download.py'
--- systemimage/download.py	2013-12-13 13:55:51 +0000
+++ systemimage/download.py	2014-02-25 17:45:25 +0000
@@ -1,4 +1,4 @@
-# Copyright (C) 2013 Canonical Ltd.
+# Copyright (C) 2013-2014 Canonical Ltd.
 # Author: Barry Warsaw <[e-mail]>
 
 # This program is free software: you can redistribute it and/or modify
@@ -22,12 +22,16 @@
     ]
 
 
+import os
 import dbus
 import logging
+import tempfile
 
+from contextlib import ExitStack
 from io import StringIO
 from pprint import pformat
 from systemimage.config import config
+from systemimage.helpers import safe_remove
 from systemimage.reactor import Reactor
 
 
@@ -191,8 +195,25 @@
         for url, dst in downloads:
             print('\t{} -> {}'.format(url, dst), file=fp)
         log.info('{}'.format(fp.getvalue()))
+        # As a workaround for LP: #1277589, ask u-d-m to download the files to
+        # .tmp files, and if they succeed, then atomically move them into
+        # their real location.
+        renames = []
+        requests = []
+        for url, dst in downloads:
+            head, tail = os.path.split(dst)
+            fd, path = tempfile.mkstemp(suffix='.tmp', prefix='', dir=head)
+            os.close(fd)
+            renames.append((path, dst))
+            requests.append((url, path, ''))
+        # mkstemp() creates the file system path, but if the files exist when
+        # the group download is requested, ubuntu-download-manager will
+        # complain and return an error.  So, delete all temporary files now so
+        # udm has a clear path to download to.
+        for path, dst in renames:
+            os.remove(path)
         object_path = iface.createDownloadGroup(
-            [(url, dst, '') for url, dst in downloads],
+            requests,     # The temporary requests.
             '',           # No hashes yet.
             False,        # Don't allow GSM yet.
             # https://bugs.freedesktop.org/show_bug.cgi?id=55594
@@ -220,6 +241,19 @@
             raise Canceled
         if reactor.timed_out:
             raise TimeoutError
+        # Now that everything succeeded, rename the temporary files.  Just to
+        # be extra cautious, set up a context manager to safely remove all
+        # temporary files in case of an error.  If there are no errors, then
+        # there will be nothing to remove.
+        with ExitStack() as resources:
+            for tmp, dst in renames:
+                resources.callback(safe_remove, tmp)
+            for tmp, dst in renames:
+                os.rename(tmp, dst)
+            # We only get here if all the renames succeeded, so there will be
+            # no temporary files to remove, so we can throw away the new
+            # ExitStack, which holds all the removals.
+            resources.pop_all()
 
     def cancel(self):
         """Cancel any current downloads."""

=== modified file 'systemimage/gpg.py'
--- systemimage/gpg.py	2013-12-13 13:55:51 +0000
+++ systemimage/gpg.py	2014-02-25 17:45:25 +0000
@@ -1,4 +1,4 @@
-# Copyright (C) 2013 Canonical Ltd.
+# Copyright (C) 2013-2014 Canonical Ltd.
 # Author: Barry Warsaw <[e-mail]>
 
 # This program is free software: you can redistribute it and/or modify
@@ -23,6 +23,7 @@
 
 import os
 import gnupg
+import hashlib
 import tarfile
 
 from contextlib import ExitStack
@@ -37,10 +38,70 @@
     always returns a boolean.  This exception is used by other functions to
     signal that a .asc file did not match.
     """
+    def __init__(self, signature_path, data_path,
+                 keyrings=None, blacklist=None):
+        super().__init__()
+        self.signature_path = signature_path
+        self.data_path = data_path
+        self.keyrings = ([] if keyrings is None else keyrings)
+        self.blacklist = blacklist
+        # We have to calculate the checksums now, because it's possible that
+        # the files will be temporary/atomic files, deleted when a context
+        # manager exits.  I.e. the files aren't guaranteed to exist after this
+        # constructor runs.
+        #
+        # Also, md5 is fine; this is not a security critical context, we just
+        # want to be able to quickly and easily compare the file on disk
+        # against the file on the server.
+        with open(self.signature_path, 'rb') as fp:
+            self.signature_checksum =  hashlib.md5(fp.read()).hexdigest()
+        with open(self.data_path, 'rb') as fp:
+            self.data_checksum = hashlib.md5(fp.read()).hexdigest()
+        self.keyring_checksums = []
+        for path in self.keyrings:
+            with open(path, 'rb') as fp:
+                checksum = hashlib.md5(fp.read()).hexdigest()
+                self.keyring_checksums.append(checksum)
+        if self.blacklist is None:
+            self.blacklist_checksum = None
+        else:
+            with open(self.blacklist, 'rb') as fp:
+                self.blacklist_checksum = hashlib.md5(fp.read()).hexdigest()
+
+    def __str__(self):
+        if self.blacklist is None:
+            checksum_str = 'no blacklist'
+            path_str = ''
+        else:
+            checksum_str = self.blacklist_checksum
+            path_str = self.blacklist
+        return """
+    sig path : {0.signature_checksum}
+               {0.signature_path}
+    data path: {0.data_checksum}
+               {0.data_path}
+    keyrings : {0.keyring_checksums}
+               {1}
+    blacklist: {2} {3}
+""".format(self, list(self.keyrings), checksum_str, path_str)
+
 
 
 class Context:
     def __init__(self, *keyrings, blacklist=None):
+        """Create a GPG signature verification context.
+
+        :param keyrings: The list of keyrings to use for validating the
+            signature on data files.
+        :type keyrings: Sequence of .tar.xz keyring files, which will be
+            unpacked to retrieve the actual .gpg keyring file.
+        :param blacklist: The blacklist keyring, from which fingerprints to
+            explicitly disallow are retrieved.
+        :type blacklist: A .tar.xz keyring file, which will be unpacked to
+            retrieve the actual .gpg keyring file.
+        """
+        self.keyring_paths = keyrings
+        self.blacklist_path = blacklist
         self._ctx = None
         self._stack = ExitStack()
         self._keyrings = []
@@ -112,6 +173,21 @@
         return set(info['keyid'] for info in self._ctx.list_keys())
 
     def verify(self, signature_path, data_path):
+        """Verify a GPG signature.
+
+        This verifies that the data file signature is valid, given the
+        keyrings and blacklist specified in the constructor.  Specifically, we
+        use GPG to extract the fingerprint in the signature path, and compare
+        it against the fingerprints in the keyrings, subtracting any
+        fingerprints in the blacklist.
+
+        :param signature_path: The file system path to the detached signature
+            file for the data file.
+        :type signature_path: str
+        :param data_path: The file system path to the data file.
+        :type data_path: str
+        :return: bool
+        """
         with open(signature_path, 'rb') as sig_fp:
             verified = self._ctx.verify_file(sig_fp, data_path)
         # If the file is properly signed, we'll be able to get back a set of
@@ -120,3 +196,21 @@
         # loaded-up keyrings.  If so, the signature succeeds.
         return verified.fingerprint in (self.fingerprints -
                                         self._blacklisted_fingerprints)
+
+    def validate(self, signature_path, data_path):
+        """Like .verify() but raises a SignatureError when invalid.
+
+        :param signature_path: The file system path to the detached signature
+            file for the data file.
+        :type signature_path: str
+        :param data_path: The file system path to the data file.
+        :type data_path: str
+        :return: None
+        :raises SignatureError: when the signature cannot be verified.  Note
+            that the exception will contain extra information, namely the
+            keyrings involved in the verification, as well as the blacklist
+            file if there is one.
+        """
+        if not self.verify(signature_path, data_path):
+            raise SignatureError(signature_path, data_path,
+                                 self.keyring_paths, self.blacklist_path)

=== modified file 'systemimage/helpers.py'
--- systemimage/helpers.py	2013-12-13 13:55:51 +0000
+++ systemimage/helpers.py	2014-02-25 17:45:25 +0000
@@ -1,4 +1,4 @@
-# Copyright (C) 2013 Canonical Ltd.
+# Copyright (C) 2013-2014 Canonical Ltd.
 # Author: Barry Warsaw <[e-mail]>
 
 # This program is free software: you can redistribute it and/or modify

=== modified file 'systemimage/image.py'
--- systemimage/image.py	2013-12-13 13:55:51 +0000
+++ systemimage/image.py	2014-02-25 17:45:25 +0000
@@ -1,4 +1,4 @@
-# Copyright (C) 2013 Canonical Ltd.
+# Copyright (C) 2013-2014 Canonical Ltd.
 # Author: Barry Warsaw <[e-mail]>
 
 # This program is free software: you can redistribute it and/or modify

=== modified file 'systemimage/index.py'
--- systemimage/index.py	2013-12-13 13:55:51 +0000
+++ systemimage/index.py	2014-02-25 17:45:25 +0000
@@ -1,4 +1,4 @@
-# Copyright (C) 2013 Canonical Ltd.
+# Copyright (C) 2013-2014 Canonical Ltd.
 # Author: Barry Warsaw <[e-mail]>
 
 # This program is free software: you can redistribute it and/or modify

=== modified file 'systemimage/keyring.py'
--- systemimage/keyring.py	2013-12-13 13:55:51 +0000
+++ systemimage/keyring.py	2014-02-25 17:45:25 +0000
@@ -1,4 +1,4 @@
-# Copyright (C) 2013 Canonical Ltd.
+# Copyright (C) 2013-2014 Canonical Ltd.
 # Author: Barry Warsaw <[e-mail]>
 
 # This program is free software: you can redistribute it and/or modify
@@ -31,7 +31,7 @@
 from datetime import datetime, timezone
 from systemimage.config import config
 from systemimage.download import DBusDownloadManager
-from systemimage.gpg import Context, SignatureError
+from systemimage.gpg import Context
 from systemimage.helpers import makedirs, safe_remove
 from urllib.parse import urljoin
 
@@ -110,8 +110,7 @@
         stack.callback(os.remove, ascxz_dst)
         signing_keyring = getattr(config.gpg, sigkr.replace('-', '_'))
         with Context(signing_keyring, blacklist=blacklist) as ctx:
-            if not ctx.verify(ascxz_dst, tarxz_dst):
-                raise SignatureError
+            ctx.validate(ascxz_dst, tarxz_dst)
         # The signature is good, so now unpack the tarball, load the json file
         # and verify its contents.
         keyring_gpg = os.path.join(config.tempdir, 'keyring.gpg')

=== modified file 'systemimage/logging.py'
--- systemimage/logging.py	2013-12-13 13:55:51 +0000
+++ systemimage/logging.py	2014-02-25 17:45:25 +0000
@@ -1,4 +1,4 @@
-# Copyright (C) 2013 Canonical Ltd.
+# Copyright (C) 2013-2014 Canonical Ltd.
 # Author: Barry Warsaw <[e-mail]>
 
 # This program is free software: you can redistribute it and/or modify
@@ -36,12 +36,35 @@
 LOGFILE_PERMISSIONS = stat.S_IRUSR | stat.S_IWUSR
 
 
+# We want to support {}-style logging for all systemimage child loggers.  One
+# way to do this is with a LogRecord factory, but to play nice with third
+# party loggers which might be using %-style, we have to make sure that we use
+# the default factory for everything else.
+#
+# This actually isn't the best way to do this because it still makes a global
+# change and we don't know how this will interact with other third party
+# loggers.  A marginally better way to do this is to pass class instances to
+# the logging calls.  Those instances would have a __str__() method that does
+# the .format() conversion.  The problem with that is that it's a bit less
+# convenient to make the logging calls because you can't pass strings
+# directly.  One such suggestion at <http://tinyurl.com/pjjwjxq> is to import
+# the class as __ (i.e. double underscore) so your logging calls would look
+# like: log.error(__('Message with {} {}'), foo, bar)
+
 class FormattingLogRecord(logging.LogRecord):
+    def __init__(self, name, *args, **kws):
+        logger_path = name.split('.')
+        self._use_format = (logger_path[0] == 'systemimage')
+        super().__init__(name, *args, **kws)
+
     def getMessage(self):
-        msg = str(self.msg)
-        if self.args:
-            msg = msg.format(*self.args)
-        return msg
+        if self._use_format:
+            msg = str(self.msg)
+            if self.args:
+                msg = msg.format(*self.args)
+            return msg
+        else:
+            return super().getMessage()
 
 
 def initialize(*, verbosity=0):
@@ -53,9 +76,7 @@
         3: logging.CRITICAL,
         }.get(verbosity, logging.ERROR)
     level = min(level, config.system.loglevel)
-    # We're not going to propagate to the root logger anyway.
-    logging.basicConfig(style='{')
-    # Make sure logging uses {}-style messages.
+    # Make sure our library's logging uses {}-style messages.
     logging.setLogRecordFactory(FormattingLogRecord)
     # Now configure the application level logger based on the ini file.
     log = logging.getLogger('systemimage')

=== modified file 'systemimage/main.py'
--- systemimage/main.py	2013-12-13 13:55:51 +0000
+++ systemimage/main.py	2014-02-25 17:45:25 +0000
@@ -1,4 +1,4 @@
-# Copyright (C) 2013 Canonical Ltd.
+# Copyright (C) 2013-2014 Canonical Ltd.
 # Author: Barry Warsaw <[e-mail]>
 
 # This program is free software: you can redistribute it and/or modify

=== modified file 'systemimage/reactor.py'
--- systemimage/reactor.py	2013-12-13 13:55:51 +0000
+++ systemimage/reactor.py	2014-02-25 17:45:25 +0000
@@ -1,4 +1,4 @@
-# Copyright (C) 2013 Canonical Ltd.
+# Copyright (C) 2013-2014 Canonical Ltd.
 # Author: Barry Warsaw <[e-mail]>
 
 # This program is free software: you can redistribute it and/or modify

=== modified file 'systemimage/reboot.py'
--- systemimage/reboot.py	2013-12-13 13:55:51 +0000
+++ systemimage/reboot.py	2014-02-25 17:45:25 +0000
@@ -1,4 +1,4 @@
-# Copyright (C) 2013 Canonical Ltd.
+# Copyright (C) 2013-2014 Canonical Ltd.
 # Author: Barry Warsaw <[e-mail]>
 
 # This program is free software: you can redistribute it and/or modify

=== modified file 'systemimage/scores.py'
--- systemimage/scores.py	2013-12-13 13:55:51 +0000
+++ systemimage/scores.py	2014-02-25 17:45:25 +0000
@@ -1,4 +1,4 @@
-# Copyright (C) 2013 Canonical Ltd.
+# Copyright (C) 2013-2014 Canonical Ltd.
 # Author: Barry Warsaw <[e-mail]>
 
 # This program is free software: you can redistribute it and/or modify

=== modified file 'systemimage/service.py'
--- systemimage/service.py	2013-12-13 13:55:51 +0000
+++ systemimage/service.py	2014-02-25 17:45:25 +0000
@@ -1,4 +1,4 @@
-# Copyright (C) 2013 Canonical Ltd.
+# Copyright (C) 2013-2014 Canonical Ltd.
 # Author: Barry Warsaw <[e-mail]>
 
 # This program is free software: you can redistribute it and/or modify
@@ -28,10 +28,9 @@
 
 from contextlib import ExitStack
 from dbus.mainloop.glib import DBusGMainLoop
-from dbus.service import BusName
 from pkg_resources import resource_string as resource_bytes
 from systemimage.config import config
-from systemimage.dbus import Loop, Service
+from systemimage.dbus import Loop
 from systemimage.helpers import makedirs
 from systemimage.logging import initialize
 from systemimage.main import DEFAULT_CONFIG_FILE
@@ -92,12 +91,20 @@
     initialize(verbosity=args.verbose)
     log = logging.getLogger('systemimage')
 
-    log.info('SystemImage dbus main loop started [{}/{}]',
-             config.channel, config.device)
     DBusGMainLoop(set_as_default=True)
 
     system_bus = dbus.SystemBus()
-    bus_name = BusName('com.canonical.SystemImage', system_bus)
+    # Ensure we're the only owner of this bus name.
+    code = system_bus.request_name(
+        'com.canonical.SystemImage',
+        dbus.bus.NAME_FLAG_DO_NOT_QUEUE)
+    if code == dbus.bus.REQUEST_NAME_REPLY_EXISTS:
+        # Another instance already owns this name.  Exit.
+        log.error('Cannot get exclusive ownership of bus name.')
+        sys.exit(2)
+
+    log.info('SystemImage dbus main loop starting [{}/{}]',
+             config.channel, config.device)
 
     with ExitStack() as stack:
         loop = Loop()
@@ -107,6 +114,7 @@
             config.dbus_service = get_service(
                 testing_mode, system_bus, '/Service', loop)
         else:
+            from systemimage.dbus import Service
             config.dbus_service = Service(system_bus, '/Service', loop)
         try:
             loop.run()

=== modified file 'systemimage/settings.py'
--- systemimage/settings.py	2013-12-13 13:55:51 +0000
+++ systemimage/settings.py	2014-02-25 17:45:25 +0000
@@ -1,4 +1,4 @@
-# Copyright (C) 2013 Canonical Ltd.
+# Copyright (C) 2013-2014 Canonical Ltd.
 # Author: Barry Warsaw <[e-mail]>
 
 # This program is free software: you can redistribute it and/or modify

=== modified file 'systemimage/state.py'
--- systemimage/state.py	2013-12-13 13:55:51 +0000
+++ systemimage/state.py	2014-02-25 17:45:25 +0000
@@ -1,4 +1,4 @@
-# Copyright (C) 2013 Canonical Ltd.
+# Copyright (C) 2013-2014 Canonical Ltd.
 # Author: Barry Warsaw <[e-mail]>
 
 # This program is free software: you can redistribute it and/or modify
@@ -217,7 +217,7 @@
                      urljoin(config.service.https_base, url)))
             get_keyring('blacklist', url, 'image-master')
         except SignatureError:
-            log.info('No signed blacklist found')
+            log.exception('No signed blacklist found')
             # The blacklist wasn't signed by the system image master.  Maybe
             # there's a new system image master key?  Let's find out.
             self._next.appendleft(self._get_master_key)
@@ -293,14 +293,16 @@
             # SIGNING key.  There may or may not be a blacklist.
             ctx = stack.enter_context(
                 Context(config.gpg.image_signing, blacklist=self.blacklist))
-            if not ctx.verify(asc_path, channels_path):
+            try:
+                ctx.validate(asc_path, channels_path)
+            except SignatureError:
                 # The signature on the channels.json file did not match.
                 # Maybe there's a new image signing key on the server.  If
                 # we've already downloaded a new image signing key, then
                 # there's nothing more to do but raise an exception.
                 # Otherwise, if a new key *is* found, retry the current step.
                 if count > 0:
-                    raise SignatureError(channels_path)
+                    raise
                 self._next.appendleft(self._get_signing_key)
                 log.info('channels.json not properly signed')
                 return
@@ -398,10 +400,7 @@
                 keyrings.append(config.gpg.device_signing)
             ctx = stack.enter_context(
                 Context(*keyrings, blacklist=self.blacklist))
-            if not ctx.verify(asc_path, index_path):
-                log.error('index.json signature failure: {} {}',
-                          index_path, asc_path)
-                raise SignatureError(index_path)
+            ctx.validate(asc_path, index_path)
             # The signature was good.
             with open(index_path, encoding='utf-8') as fp:
                 self.index = Index.from_json(fp.read())
@@ -512,8 +511,7 @@
             # Verify the signatures on all the downloaded files.
             with Context(*keyrings, blacklist=self.blacklist) as ctx:
                 for dst, asc in signatures:
-                    if not ctx.verify(asc, dst):
-                        raise SignatureError(dst)
+                    ctx.validate(asc, dst)
             # Verify the checksums.
             for dst, checksum in checksums:
                 with open(dst, 'rb') as fp:

=== modified file 'systemimage/testing/controller.py'
--- systemimage/testing/controller.py	2013-12-13 13:55:51 +0000
+++ systemimage/testing/controller.py	2014-02-25 17:45:25 +0000
@@ -1,4 +1,4 @@
-# Copyright (C) 2013 Canonical Ltd.
+# Copyright (C) 2013-2014 Canonical Ltd.
 # Author: Barry Warsaw <[e-mail]>
 
 # This program is free software: you can redistribute it and/or modify
@@ -25,8 +25,8 @@
 import pwd
 import sys
 import dbus
+import time
 import psutil
-import signal
 import subprocess
 
 from contextlib import ExitStack
@@ -38,6 +38,8 @@
 
 
 SPACE = ' '
+OVERRIDE = os.environ.get('SYSTEMIMAGE_DBUS_DAEMON_HUP_SLEEP_SECONDS')
+HUP_SLEEP = (0 if OVERRIDE is None else int(OVERRIDE))
 
 
 def start_system_image(controller):
@@ -125,7 +127,7 @@
 class Controller:
     """Start and stop D-Bus service under test."""
 
-    def __init__(self):
+    def __init__(self, logfile=None):
         # Non-public.
         self._stack = ExitStack()
         self._stoppers = []
@@ -148,21 +150,22 @@
         # We need a client.ini file for the subprocess.
         ini_tmpdir = self._stack.enter_context(temporary_directory())
         ini_vardir = self._stack.enter_context(temporary_directory())
+        ini_logfile = (os.path.join(ini_tmpdir, 'client.log')
+                       if logfile is None
+                       else logfile)
         self.ini_path = os.path.join(self.tmpdir, 'client.ini')
         template = resource_bytes(
             'systemimage.tests.data', 'config_03.ini').decode('utf-8')
         with open(self.ini_path, 'w', encoding='utf-8') as fp:
-            print(template.format(tmpdir=ini_tmpdir, vardir=ini_vardir),
+            print(template.format(tmpdir=ini_tmpdir, vardir=ini_vardir,
+                                  logfile=ini_logfile),
                   file=fp)
 
     def _configure_services(self):
-        # If the daemon is already running, kill all the children and HUP the
-        # daemon to reset dbus activation.
+        # If the dbus-daemon is already running, kill all the children.
         if self.daemon_pid is not None:
             for stopper in self._stoppers:
                 stopper(self)
-            process = psutil.Process(self.daemon_pid)
-            process.send_signal(signal.SIGHUP)
         del self._stoppers[:]
         # Now we have to set up the .service files.  We use the Python
         # executable used to run the tests, executing the entry point as would
@@ -178,6 +181,12 @@
             with open(service_path, 'w', encoding='utf-8') as fp:
                 fp.write(config)
             self._stoppers.append(stopper)
+        # If the dbus-daemon is running, reload its configuration files.
+        if self.daemon_pid is not None:
+            service = dbus.SystemBus().get_object('org.freedesktop.DBus', '/')
+            iface = dbus.Interface(service, 'org.freedesktop.DBus')
+            iface.ReloadConfig()
+            time.sleep(HUP_SLEEP)
 
     def set_mode(self, *, cert_pem=None, service_mode=''):
         self.mode = service_mode

=== modified file 'systemimage/testing/dbus.py'
--- systemimage/testing/dbus.py	2013-12-13 13:55:51 +0000
+++ systemimage/testing/dbus.py	2014-02-25 17:45:25 +0000
@@ -1,4 +1,4 @@
-# Copyright (C) 2013 Canonical Ltd.
+# Copyright (C) 2013-2014 Canonical Ltd.
 # Author: Barry Warsaw <[e-mail]>
 
 # This program is free software: you can redistribute it and/or modify
@@ -31,6 +31,8 @@
 from systemimage.helpers import makedirs, safe_remove
 from unittest.mock import patch
 
+from systemimage.testing.helpers import debug
+
 
 SPACE = ' '
 SIGNAL_DELAY_SECS = 5
@@ -65,7 +67,11 @@
     @method('com.canonical.SystemImage')
     def Reset(self):
         self._api = Mediator()
-        self._checking = False
+        try:
+            self._checking.release()
+        except RuntimeError:
+            # Lock is already released.
+            pass
         self._update = None
         self._downloading = False
         self._rebootable = False

=== modified file 'systemimage/testing/demo.py'
--- systemimage/testing/demo.py	2013-12-13 13:55:51 +0000
+++ systemimage/testing/demo.py	2014-02-25 17:45:25 +0000
@@ -1,4 +1,4 @@
-# Copyright (C) 2013 Canonical Ltd.
+# Copyright (C) 2013-2014 Canonical Ltd.
 # Author: Barry Warsaw <[e-mail]>
 
 # This program is free software: you can redistribute it and/or modify

=== modified file 'systemimage/testing/helpers.py'
--- systemimage/testing/helpers.py	2013-12-13 13:55:51 +0000
+++ systemimage/testing/helpers.py	2014-02-25 17:45:25 +0000
@@ -1,4 +1,4 @@
-# Copyright (C) 2013 Canonical Ltd.
+# Copyright (C) 2013-2014 Canonical Ltd.
 # Author: Barry Warsaw <[e-mail]>
 
 # This program is free software: you can redistribute it and/or modify
@@ -107,6 +107,12 @@
             # Please shut up.
             pass
 
+        def handle_one_request(self):
+            try:
+                super().handle_one_request()
+            except ConnectionResetError:
+                super().handle_one_request()
+
         def do_GET(self):
             # If we requested the magic 'user-agent.txt' file, send back the
             # value of the User-Agent header.  Otherwise, vend as normal.
@@ -166,7 +172,16 @@
             for conn in connections:
                 if conn.fileno() != -1:
                     # Disallow sends and receives.
-                    conn.shutdown(SHUT_RDWR)
+                    try:
+                        conn.shutdown(SHUT_RDWR)
+                    except OSError:
+                        # I'm ignoring all OSErrors here, although the only
+                        # one I've seen semi-consistency is ENOTCONN [107]
+                        # "Transport endpoint is not connected".  I don't know
+                        # why this happens, but it tells me that the client
+                        # has already exited.  We're shutting down, so who
+                        # cares?  (Or am I masking a real error?)
+                        pass
                 conn.close()
             server.shutdown()
             thread.join()
@@ -332,7 +347,7 @@
         setup_keyring_txz(keyring + '.gpg', signing_kr, json_data, dst)
 
 
-def setup_index(index, todir, keyring):
+def setup_index(index, todir, keyring, write_callback=None):
     for image in get_index(index).images:
         for filerec in image.files:
             path = (filerec.path[1:]
@@ -340,10 +355,13 @@
                     else filerec.path)
             dst = os.path.join(todir, path)
             makedirs(os.path.dirname(dst))
-            contents = EMPTYSTRING.join(
-                os.path.splitext(filerec.path)[0].split('/'))
-            with open(dst, 'w', encoding='utf-8') as fp:
-                fp.write(contents)
+            if write_callback is None:
+                contents = EMPTYSTRING.join(
+                    os.path.splitext(filerec.path)[0].split('/'))
+                with open(dst, 'w', encoding='utf-8') as fp:
+                    fp.write(contents)
+            else:
+                write_callback(dst)
             # Sign with the specified signing key.
             sign(dst, keyring)
 

=== modified file 'systemimage/testing/nose.py'
--- systemimage/testing/nose.py	2013-12-13 13:55:51 +0000
+++ systemimage/testing/nose.py	2014-02-25 17:45:25 +0000
@@ -1,4 +1,4 @@
-# Copyright (C) 2013 Canonical Ltd.
+# Copyright (C) 2013-2014 Canonical Ltd.
 # Author: Barry Warsaw <[e-mail]>
 
 # This program is free software: you can redistribute it and/or modify
@@ -75,15 +75,24 @@
         super().__init__()
         self.patterns = []
         self.verbosity = 0
+        self.log_file = None
         self.addArgument(self.patterns, 'P', 'pattern',
                          'Add a test matching pattern')
         def bump(ignore):
             self.verbosity += 1
         self.addFlag(bump, 'V', 'Verbosity',
                      'Increase system-image verbosity')
+        def set_log_file(path):
+            self.log_file = path[0]
+        self.addOption(set_log_file, 'L', 'logfile',
+                       'Set the log file for the test run',
+                       nargs=1)
 
     @configuration
     def startTestRun(self, event):
+        from systemimage.config import config
+        if self.log_file is not None:
+            config.system.logfile = self.log_file
         DBusGMainLoop(set_as_default=True)
         initialize(verbosity=self.verbosity)
         # We need to set up the dbus service controller, since all the tests
@@ -92,7 +101,7 @@
         # individual services, and we can write new dbus configuration files
         # and HUP the dbus-launch to re-read them, but we cannot change bus
         # addresses after the initial one is set.
-        SystemImagePlugin.controller = Controller()
+        SystemImagePlugin.controller = Controller(self.log_file)
         SystemImagePlugin.controller.start()
         atexit.register(SystemImagePlugin.controller.stop)
 
@@ -123,3 +132,13 @@
         SystemImagePlugin.controller.stop()
         # Let other plugins continue printing.
         return None
+
+    ## def startTest(self, event):
+    ##     from systemimage.testing.helpers import debug
+    ##     with debug() as dlog:
+    ##         dlog('vvvvv', event.test)
+
+    ## def stopTest(self, event):
+    ##     from systemimage.testing.helpers import debug
+    ##     with debug() as dlog:
+    ##         dlog('^^^^^', event.test)

=== modified file 'systemimage/tests/data/config_03.ini'
--- systemimage/tests/data/config_03.ini	2013-12-13 13:55:51 +0000
+++ systemimage/tests/data/config_03.ini	2014-02-25 17:45:25 +0000
@@ -14,7 +14,7 @@
 timeout: 1s
 build_file: {tmpdir}/ubuntu-build
 tempdir: {tmpdir}/tmp
-logfile: {tmpdir}/client.log
+logfile: {logfile}
 loglevel: info
 settings_db: {vardir}/settings.db
 

=== added file 'systemimage/tests/data/index_24.json'
--- systemimage/tests/data/index_24.json	1970-01-01 00:00:00 +0000
+++ systemimage/tests/data/index_24.json	2014-02-25 17:45:25 +0000
@@ -0,0 +1,36 @@
+{
+    "global": {
+        "generated_at": "Thu Aug 01 08:01:00 UTC 2013"
+    },
+    "images": [
+        {
+            "description": "Full",
+            "files": [
+                {
+                    "checksum": "5b05b298e974f3b9e40f0a1a8188f50984a4f18fb329e050324296632d3d9dfc",
+                    "order": 3,
+                    "path": "/3/4/5.txt",
+                    "signature": "/3/4/5.txt.asc",
+                    "size": 104857600
+                },
+                {
+                    "checksum": "5b05b298e974f3b9e40f0a1a8188f50984a4f18fb329e050324296632d3d9dfc",
+                    "order": 1,
+                    "path": "/4/5/6.txt",
+                    "signature": "/4/5/6.txt.asc",
+                    "size": 104857600
+                },
+                {
+                    "checksum": "5b05b298e974f3b9e40f0a1a8188f50984a4f18fb329e050324296632d3d9dfc",
+                    "order": 2,
+                    "path": "/5/6/7.txt",
+                    "signature": "/5/6/7.txt.asc",
+                    "size": 104857600
+                }
+            ],
+            "type": "full",
+            "version": 1600,
+            "bootme": true
+        }
+    ]
+}

=== modified file 'systemimage/tests/test_api.py'
--- systemimage/tests/test_api.py	2013-12-13 13:55:51 +0000
+++ systemimage/tests/test_api.py	2014-02-25 17:45:25 +0000
@@ -1,4 +1,4 @@
-# Copyright (C) 2013 Canonical Ltd.
+# Copyright (C) 2013-2014 Canonical Ltd.
 # Author: Barry Warsaw <[e-mail]>
 
 # This program is free software: you can redistribute it and/or modify

=== modified file 'systemimage/tests/test_bag.py'
--- systemimage/tests/test_bag.py	2013-12-13 13:55:51 +0000
+++ systemimage/tests/test_bag.py	2014-02-25 17:45:25 +0000
@@ -1,4 +1,4 @@
-# Copyright (C) 2013 Canonical Ltd.
+# Copyright (C) 2013-2014 Canonical Ltd.
 # Author: Barry Warsaw <[e-mail]>
 
 # This program is free software: you can redistribute it and/or modify

=== modified file 'systemimage/tests/test_candidates.py'
--- systemimage/tests/test_candidates.py	2013-12-13 13:55:51 +0000
+++ systemimage/tests/test_candidates.py	2014-02-25 17:45:25 +0000
@@ -1,4 +1,4 @@
-# Copyright (C) 2013 Canonical Ltd.
+# Copyright (C) 2013-2014 Canonical Ltd.
 # Author: Barry Warsaw <[e-mail]>
 
 # This program is free software: you can redistribute it and/or modify

=== modified file 'systemimage/tests/test_channel.py'
--- systemimage/tests/test_channel.py	2013-12-13 13:55:51 +0000
+++ systemimage/tests/test_channel.py	2014-02-25 17:45:25 +0000
@@ -1,4 +1,4 @@
-# Copyright (C) 2013 Canonical Ltd.
+# Copyright (C) 2013-2014 Canonical Ltd.
 # Author: Barry Warsaw <[e-mail]>
 
 # This program is free software: you can redistribute it and/or modify

=== modified file 'systemimage/tests/test_config.py'
--- systemimage/tests/test_config.py	2013-12-13 13:55:51 +0000
+++ systemimage/tests/test_config.py	2014-02-25 17:45:25 +0000
@@ -1,4 +1,4 @@
-# Copyright (C) 2013 Canonical Ltd.
+# Copyright (C) 2013-2014 Canonical Ltd.
 # Author: Barry Warsaw <[e-mail]>
 
 # This program is free software: you can redistribute it and/or modify

=== modified file 'systemimage/tests/test_dbus.py'
--- systemimage/tests/test_dbus.py	2013-12-13 13:55:51 +0000
+++ systemimage/tests/test_dbus.py	2014-02-25 17:45:25 +0000
@@ -1,4 +1,4 @@
-# Copyright (C) 2013 Canonical Ltd.
+# Copyright (C) 2013-2014 Canonical Ltd.
 # Author: Barry Warsaw <[e-mail]>
 
 # This program is free software: you can redistribute it and/or modify
@@ -23,6 +23,7 @@
     'TestDBusGetSet',
     'TestDBusInfo',
     'TestDBusInfoNoDetails',
+    'TestDBusLP1277589',
     'TestDBusMockFailApply',
     'TestDBusMockFailPause',
     'TestDBusMockFailResume',
@@ -122,6 +123,23 @@
         self.quit()
 
 
+class DoubleCheckingReactor(Reactor):
+    def __init__(self, iface):
+        super().__init__(dbus.SystemBus())
+        self.iface = iface
+        self.uas_signals = []
+        self.react_to('UpdateAvailableStatus')
+        self.react_to('UpdateDownloaded')
+        self.schedule(self.iface.CheckForUpdate)
+
+    def _do_UpdateAvailableStatus(self, signal, path, *args, **kws):
+        self.uas_signals.append(args)
+        self.schedule(self.iface.CheckForUpdate)
+
+    def _do_UpdateDownloaded(self, *args, **kws):
+        self.quit()
+
+
 class _TestBase(unittest.TestCase):
     """Base class for all DBus testing."""
 
@@ -262,13 +280,14 @@
         safe_remove(self.reboot_log)
         super().tearDown()
 
-    def _prepare_index(self, index_file):
+    def _prepare_index(self, index_file, write_callback=None):
         serverdir = SystemImagePlugin.controller.serverdir
         index_path = os.path.join(serverdir, 'stable', 'nexus7', 'index.json')
         head, tail = os.path.split(index_path)
         copy(index_file, head, tail)
         sign(index_path, 'device-signing.gpg')
-        setup_index(index_file, serverdir, 'device-signing.gpg')
+        setup_index(index_file, serverdir, 'device-signing.gpg',
+                    write_callback)
 
     def _touch_build(self, version):
         # Unlike the touch_build() helper, this one uses our own config object
@@ -374,6 +393,23 @@
         self.assertEqual(last_update_date, '2013-01-20 12:01:45')
         # All other values are undefined.
 
+    def test_check_for_update_twice(self):
+        # Issue two CheckForUpdate calls immediate after each other.
+        self.download_always()
+        reactor = SignalCapturingReactor('UpdateAvailableStatus')
+        def two_calls():
+            self.iface.CheckForUpdate()
+            self.iface.CheckForUpdate()
+        reactor.run(two_calls)
+        self.assertEqual(len(reactor.signals), 1)
+        # There's one boolean argument to the result.
+        (is_available, downloading, available_version, update_size,
+         last_update_date,
+         # descriptions,
+         error_reason) = reactor.signals[0]
+        self.assertTrue(is_available)
+        self.assertTrue(downloading)
+
     @unittest.skip('LP: #1215586')
     def test_get_multilingual_descriptions(self):
         # The descriptions are multilingual.
@@ -1368,7 +1404,9 @@
     def setUp(self):
         super().setUp()
         # We have to hack the files to be rather large so that the download
-        # doesn't complete before we get a chance to pause it.
+        # doesn't complete before we get a chance to pause it.  Of course,
+        # this breaks the signatures because we're changing the file contents
+        # after the .asc files have been written.
         for path in ('3/4/5.txt', '4/5/6.txt', '5/6/7.txt'):
             full_path = os.path.join(
                 SystemImagePlugin.controller.serverdir, path)
@@ -1391,15 +1429,25 @@
         self.assertTrue(reactor.paused)
         # Now let's resume the download.  Because we intentionally corrupted
         # the downloaded files, we'll get an UpdateFailed signal instead of
-        # the successful UpdateDownloaded signal.  We can ignore that.
+        # the successful UpdateDownloaded signal.
         reactor = SignalCapturingReactor('UpdateFailed')
         reactor.run(self.iface.DownloadUpdate, timeout=60)
         self.assertEqual(len(reactor.signals), 1)
-        # We've gotten one error and the first file that failed is 5.txt.
+        # The error message will include lots of details on the SignatureError
+        # that results.  The key thing is that it's 5.txt that is the first
+        # file to fail its signature check.
         failure_count, last_error = reactor.signals[0]
         self.assertEqual(failure_count, 1)
-        # Watch out for the trailing newline.
-        self.assertEqual(os.path.basename(last_error[:-1]), '5.txt')
+        check_next = False
+        for line in last_error.splitlines():
+            line = line.strip()
+            if check_next:
+                self.assertEqual(os.path.basename(line), '5.txt')
+                break
+            if line.startswith('data path:'):
+                check_next = True
+        else:
+            raise AssertionError('Did not find expected error output')
 
 
 class TestDBusUseCache(_LiveTesting):
@@ -1513,3 +1561,45 @@
 update 5.txt 5.txt.asc
 unmount system
 """)
+
+
+class TestDBusLP1277589(_LiveTesting):
+    def test_multiple_check_for_updates(self):
+        # Log analysis of LP: #1277589 appears to show the following scenario,
+        # reproduced in this test case:
+        #
+        # * Automatic updates are enabled.
+        # * No image signing or image master keys are present.
+        # * A full update is checked.
+        #   - A new image master key and image signing key is downloaded.
+        #   - Update is available
+        #
+        # Start by creating some big files which will take a while to
+        # download.
+        def write_callback(dst):
+            # Write a 100 MiB sized file.
+            with open(dst, 'wb') as fp:
+                for i in range(25600):
+                    fp.write(b'x' * 4096)
+        self._prepare_index('index_24.json', write_callback)
+        # Create a reactor that will exit when the UpdateDownloaded signal is
+        # received.  We're going to issue a CheckForUpdate with automatic
+        # updates enabled.  As soon as we receive the UpdateAvailableStatus
+        # signal, we'll immediately issue *another* CheckForUpdate, which
+        # should run while the auto-download is working.
+        #
+        # At the end, we should not get another UpdateAvailableStatus signal,
+        # but we should get the UpdateDownloaded signal.
+        reactor = DoubleCheckingReactor(self.iface)
+        reactor.run()
+        self.assertEqual(len(reactor.uas_signals), 1)
+        (is_available, downloading, available_version, update_size,
+         last_update_date,
+         #descriptions,
+         error_reason) = reactor.uas_signals[0]
+        self.assertTrue(is_available)
+        self.assertTrue(downloading)
+        self.assertEqual(available_version, '1600')
+        self.assertEqual(update_size, 314572800)
+        self.assertEqual(last_update_date, 'Unknown')
+        self.assertEqual(error_reason, '')

=== modified file 'systemimage/tests/test_download.py'
--- systemimage/tests/test_download.py	2013-12-13 13:55:51 +0000
+++ systemimage/tests/test_download.py	2014-02-25 17:45:25 +0000
@@ -1,4 +1,4 @@
-# Copyright (C) 2013 Canonical Ltd.
+# Copyright (C) 2013-2014 Canonical Ltd.
 # Author: Barry Warsaw <[e-mail]>
 
 # This program is free software: you can redistribute it and/or modify

=== modified file 'systemimage/tests/test_gpg.py'
--- systemimage/tests/test_gpg.py	2013-12-13 13:55:51 +0000
+++ systemimage/tests/test_gpg.py	2014-02-25 17:45:25 +0000
@@ -1,4 +1,4 @@
-# Copyright (C) 2013 Canonical Ltd.
+# Copyright (C) 2013-2014 Canonical Ltd.
 # Author: Barry Warsaw <[e-mail]>
 
 # This program is free software: you can redistribute it and/or modify
@@ -18,15 +18,20 @@
 __all__ = [
     'TestKeyrings',
     'TestSignature',
+    'TestSignatureError',
     ]
 
 
 import os
+import sys
+import hashlib
 import unittest
+import traceback
 
 from contextlib import ExitStack
+from io import StringIO
 from systemimage.config import config
-from systemimage.gpg import Context
+from systemimage.gpg import Context, SignatureError
 from systemimage.helpers import temporary_directory
 from systemimage.testing.helpers import (
     configuration, copy, setup_keyring_txz, setup_keyrings, sign)
@@ -330,3 +335,171 @@
             with Context(keyring_1, keyring_2, blacklist=blacklist) as ctx:
                 self.assertFalse(
                     ctx.verify(channels_json + '.asc', channels_json))
+
+    @configuration
+    def test_good_validation(self):
+        # The .validate() method does nothing if the signature is good.
+        channels_json = os.path.join(self._tmpdir, 'channels.json')
+        copy('channels_01.json', self._tmpdir, dst=channels_json)
+        sign(channels_json, 'image-signing.gpg')
+        with temporary_directory() as tmpdir:
+            keyring = os.path.join(tmpdir, 'image-signing.tar.xz')
+            setup_keyring_txz('image-signing.gpg', 'image-master.gpg',
+                              dict(type='image-signing'), keyring)
+            with Context(keyring) as ctx:
+                self.assertIsNone(
+                    ctx.validate(channels_json + '.asc', channels_json))
+
+
+class TestSignatureError(unittest.TestCase):
+    def setUp(self):
+        self._stack = ExitStack()
+        self._tmpdir = self._stack.enter_context(temporary_directory())
+
+    def tearDown(self):
+        self._stack.close()
+
+    def test_extra_data(self):
+        # A SignatureError includes extra information about the path to the
+        # signature file, and the path to the data file.  You also get the md5
+        # checksums of those two paths.
+        signature_path = os.path.join(self._tmpdir, 'signature')
+        data_path = os.path.join(self._tmpdir, 'data')
+        with open(signature_path, 'wb') as fp:
+            fp.write(b'012345')
+        with open(data_path, 'wb') as fp:
+            fp.write(b'67890a')
+        error = SignatureError(signature_path, data_path)
+        self.assertEqual(error.signature_path, signature_path)
+        self.assertEqual(error.data_path, data_path)
+        self.assertEqual(
+            error.signature_checksum, 'd6a9a933c8aafc51e55ac0662b6e4d4a')
+        self.assertEqual(
+            error.data_checksum, 'e82780258de250078f7ad3f595d71f6d')
+
+    @configuration
+    def test_signature_invalid(self):
+        # The .validate() method raises a SignatureError exception with extra
+        # information when the signature is invalid.
+        channels_json = os.path.join(self._tmpdir, 'channels.json')
+        copy('channels_01.json', self._tmpdir, dst=channels_json)
+        sign(channels_json, 'device-signing.gpg')
+        # Verify the signature with the pubkey.
+        with temporary_directory() as tmpdir:
+            dst = os.path.join(tmpdir, 'image-signing.tar.xz')
+            setup_keyring_txz('image-signing.gpg', 'image-master.gpg',
+                              dict(type='image-signing'), dst)
+            # Get the dst's checksum now, because the file will get deleted
+            # when the tmpdir context manager exits.
+            with open(dst, 'rb') as fp:
+                dst_checksum = hashlib.md5(fp.read()).hexdigest()
+            with Context(dst) as ctx:
+                with self.assertRaises(SignatureError) as cm:
+                    ctx.validate(channels_json + '.asc', channels_json)
+        error = cm.exception
+        basename = os.path.basename
+        self.assertEqual(basename(error.signature_path), 'channels.json.asc')
+        self.assertEqual(basename(error.data_path), 'channels.json')
+        # The contents of the signature file are not predictable.
+        with open(channels_json + '.asc', 'rb') as fp:
+            checksum = hashlib.md5(fp.read()).hexdigest()
+        self.assertEqual(error.signature_checksum, checksum)
+        self.assertEqual(
+            error.data_checksum, '715c63fecbf44b62f9fa04a82dfa7d29')
+        basenames = [basename(path) for path in error.keyrings]
+        self.assertEqual(basenames, ['image-signing.tar.xz'])
+        self.assertIsNone(error.blacklist)
+        self.assertEqual(error.keyring_checksums, [dst_checksum])
+        self.assertIsNone(error.blacklist_checksum)
+
+    @configuration
+    def test_signature_invalid_due_to_blacklist(self):
+        # Like above, but we put the device signing key id in the blacklist.
+        channels_json = os.path.join(self._tmpdir, 'channels.json')
+        copy('channels_01.json', self._tmpdir, dst=channels_json)
+        sign(channels_json, 'device-signing.gpg')
+        # Verify the signature with the pubkey.
+        with temporary_directory() as tmpdir:
+            keyring_1 = os.path.join(tmpdir, 'image-signing.tar.xz')
+            keyring_2 = os.path.join(tmpdir, 'device-signing.tar.xz')
+            blacklist = os.path.join(tmpdir, 'blacklist.tar.xz')
+            setup_keyring_txz('image-signing.gpg', 'image-master.gpg',
+                              dict(type='image-signing'), keyring_1)
+            setup_keyring_txz('device-signing.gpg', 'image-signing.gpg',
+                              dict(type='device-signing'), keyring_2)
+            # We're letting the device signing pubkey stand in for a blacklist.
+            setup_keyring_txz('device-signing.gpg', 'image-master.gpg',
+                              dict(type='blacklist'), blacklist)
+            # Get the keyring checksums now, because the files will get
+            # deleted when the tmpdir context manager exits.
+            keyring_checksums = []
+            for path in (keyring_1, keyring_2):
+                with open(path, 'rb') as fp:
+                    checksum = hashlib.md5(fp.read()).hexdigest()
+                keyring_checksums.append(checksum)
+            with open(blacklist, 'rb') as fp:
+                blacklist_checksum = hashlib.md5(fp.read()).hexdigest()
+            with Context(keyring_1, keyring_2, blacklist=blacklist) as ctx:
+                with self.assertRaises(SignatureError) as cm:
+                    ctx.validate(channels_json + '.asc', channels_json)
+        error = cm.exception
+        basename = os.path.basename
+        self.assertEqual(basename(error.signature_path), 'channels.json.asc')
+        self.assertEqual(basename(error.data_path), 'channels.json')
+        # The contents of the signature file are not predictable.
+        with open(channels_json + '.asc', 'rb') as fp:
+            checksum = hashlib.md5(fp.read()).hexdigest()
+        self.assertEqual(error.signature_checksum, checksum)
+        self.assertEqual(
+            error.data_checksum, '715c63fecbf44b62f9fa04a82dfa7d29')
+        basenames = [basename(path) for path in error.keyrings]
+        self.assertEqual(basenames, ['image-signing.tar.xz',
+                                     'device-signing.tar.xz'])
+        self.assertEqual(basename(error.blacklist), 'blacklist.tar.xz')
+        self.assertEqual(error.keyring_checksums, keyring_checksums)
+        self.assertEqual(error.blacklist_checksum, blacklist_checksum)
+
+    @configuration
+    def test_signature_error_logging(self):
+        # The repr/str of the SignatureError should contain lots of useful
+        # information that will make debugging easier.
+        channels_json = os.path.join(self._tmpdir, 'channels.json')
+        copy('channels_01.json', self._tmpdir, dst=channels_json)
+        sign(channels_json, 'device-signing.gpg')
+        # Verify the signature with the pubkey.
+        tmpdir = self._stack.enter_context(temporary_directory())
+        dst = os.path.join(tmpdir, 'image-signing.tar.xz')
+        setup_keyring_txz('image-signing.gpg', 'image-master.gpg',
+                          dict(type='image-signing'), dst)
+        output = StringIO()
+        with Context(dst) as ctx:
+            try:
+                ctx.validate(channels_json + '.asc', channels_json)
+            except SignatureError:
+                # For our purposes, log.exception() is essentially a wrapper
+                # around this traceback call.  We don't really care about the
+                # full stack trace though.
+                e = sys.exc_info()
+                traceback.print_exception(e[0], e[1], e[2],
+                                          limit=0, file=output)
+        # 2014-02-12 BAW: Yuck, but I can't get assertRegex() to work properly.
+        for i, line in enumerate(output.getvalue().splitlines()):
+            if i == 0:
+                self.assertEqual(line, 'Traceback (most recent call last):')
+            elif i == 1:
+                self.assertEqual(line, 'systemimage.gpg.SignatureError: ')
+            elif i == 2:
+                self.assertTrue(line.startswith('    sig path :'))
+            elif i == 3:
+                self.assertTrue(line.endswith('/channels.json.asc'))
+            elif i == 4:
+                self.assertEqual(
+                    line, '    data path: 715c63fecbf44b62f9fa04a82dfa7d29')
+            elif i == 5:
+                self.assertTrue(line.endswith('/channels.json'))
+            elif i == 6:
+                self.assertTrue(line.startswith('    keyrings :'))
+            elif i == 7:
+                self.assertTrue(line.endswith("/image-signing.tar.xz']"))
+            elif i == 8:
+                self.assertEqual(line, '    blacklist: no blacklist ')

=== modified file 'systemimage/tests/test_helpers.py'
--- systemimage/tests/test_helpers.py	2013-12-13 13:55:51 +0000
+++ systemimage/tests/test_helpers.py	2014-02-25 17:45:25 +0000
@@ -1,4 +1,4 @@
-# Copyright (C) 2013 Canonical Ltd.
+# Copyright (C) 2013-2014 Canonical Ltd.
 # Author: Barry Warsaw <[e-mail]>
 
 # This program is free software: you can redistribute it and/or modify

=== modified file 'systemimage/tests/test_image.py'
--- systemimage/tests/test_image.py	2013-12-13 13:55:51 +0000
+++ systemimage/tests/test_image.py	2014-02-25 17:45:25 +0000
@@ -1,4 +1,4 @@
-# Copyright (C) 2013 Canonical Ltd.
+# Copyright (C) 2013-2014 Canonical Ltd.
 # Author: Barry Warsaw <[e-mail]>
 
 # This program is free software: you can redistribute it and/or modify

=== modified file 'systemimage/tests/test_index.py'
--- systemimage/tests/test_index.py	2013-12-13 13:55:51 +0000
+++ systemimage/tests/test_index.py	2014-02-25 17:45:25 +0000
@@ -1,4 +1,4 @@
-# Copyright (C) 2013 Canonical Ltd.
+# Copyright (C) 2013-2014 Canonical Ltd.
 # Author: Barry Warsaw <[e-mail]>
 
 # This program is free software: you can redistribute it and/or modify

=== modified file 'systemimage/tests/test_keyring.py'
--- systemimage/tests/test_keyring.py	2013-12-13 13:55:51 +0000
+++ systemimage/tests/test_keyring.py	2014-02-25 17:45:25 +0000
@@ -1,4 +1,4 @@
-# Copyright (C) 2013 Canonical Ltd.
+# Copyright (C) 2013-2014 Canonical Ltd.
 # Author: Barry Warsaw <[e-mail]>
 
 # This program is free software: you can redistribute it and/or modify
@@ -22,6 +22,7 @@
 
 
 import os
+import hashlib
 import unittest
 
 from contextlib import ExitStack
@@ -174,11 +175,25 @@
         setup_keyrings()
         # Use the spare key as the blacklist, signed by itself.  Since this
         # won't match the image-signing key, the check will fail.
+        server_path = os.path.join(self._serverdir, 'gpg', 'blacklist.tar.xz')
         setup_keyring_txz(
-            'spare.gpg', 'spare.gpg', dict(type='blacklist'),
-            os.path.join(self._serverdir, 'gpg', 'blacklist.tar.xz'))
-        self.assertRaises(SignatureError, get_keyring,
-                          'blacklist', 'gpg/blacklist.tar.xz', 'image-master')
+            'spare.gpg', 'spare.gpg', dict(type='blacklist'), server_path)
+        with self.assertRaises(SignatureError) as cm:
+            get_keyring('blacklist', 'gpg/blacklist.tar.xz', 'image-master')
+        error = cm.exception
+        # The local file name will be keyring.tar.xz in the cache directory.
+        basename = os.path.basename
+        self.assertEqual(basename(error.data_path), 'keyring.tar.xz')
+        self.assertEqual(basename(error.signature_path), 'keyring.tar.xz.asc')
+        # The crafted blacklist.tar.xz file will have an unpredictable
+        # checksum due to tarfile variablility.
+        with open(server_path, 'rb') as fp:
+            checksum = hashlib.md5(fp.read()).hexdigest()
+        self.assertEqual(error.data_checksum, checksum)
+        # The signature file's checksum is also unpredictable.
+        with open(server_path + '.asc', 'rb') as fp:
+            checksum = hashlib.md5(fp.read()).hexdigest()
+        self.assertEqual(error.signature_checksum, checksum)
 
     @configuration
     def test_blacklisted_signature(self):

=== modified file 'systemimage/tests/test_main.py'
--- systemimage/tests/test_main.py	2013-12-13 13:55:51 +0000
+++ systemimage/tests/test_main.py	2014-02-25 17:45:25 +0000
@@ -1,4 +1,4 @@
-# Copyright (C) 2013 Canonical Ltd.
+# Copyright (C) 2013-2014 Canonical Ltd.
 # Author: Barry Warsaw <[e-mail]>
 
 # This program is free software: you can redistribute it and/or modify
@@ -26,11 +26,13 @@
 
 
 import os
+import sys
 import dbus
 import stat
 import time
 import shutil
 import unittest
+import subprocess
 
 from contextlib import ExitStack, contextmanager
 from datetime import datetime
@@ -781,3 +783,25 @@
         self.assertEqual(stat.filemode(mode), 'drwx--S---')
         mode = os.stat(config.system.logfile).st_mode
         self.assertEqual(stat.filemode(mode), '-rw-------')
+
+    def test_single_instance(self):
+        # Only one instance of the system-image-dbus service is allowed to
+        # remain active on a single system bus.
+        self.assertIsNone(find_dbus_process(self.ini_path))
+        self._activate()
+        proc = find_dbus_process(self.ini_path)
+        # Attempt to start a second process on the same system bus.
+        env = dict(
+            DBUS_SYSTEM_BUS_ADDRESS=os.environ['DBUS_SYSTEM_BUS_ADDRESS'])
+        args = (sys.executable, '-m', 'systemimage.service',
+                '-C', self.ini_path)
+        second = subprocess.Popen(args, universal_newlines=True, env=env)
+        # Allow a TimeoutExpired exception to fail the test.
+        try:
+            code = second.wait(timeout=10)
+        except subprocess.TimeoutExpired:
+            second.kill()
+            second.communicate()
+            raise
+        self.assertNotEqual(second.pid, proc)
+        self.assertEqual(code, 2)

=== modified file 'systemimage/tests/test_scores.py'
--- systemimage/tests/test_scores.py	2013-12-13 13:55:51 +0000
+++ systemimage/tests/test_scores.py	2014-02-25 17:45:25 +0000
@@ -1,4 +1,4 @@
-# Copyright (C) 2013 Canonical Ltd.
+# Copyright (C) 2013-2014 Canonical Ltd.
 # Author: Barry Warsaw <[e-mail]>
 
 # This program is free software: you can redistribute it and/or modify

=== modified file 'systemimage/tests/test_settings.py'
--- systemimage/tests/test_settings.py	2013-12-13 13:55:51 +0000
+++ systemimage/tests/test_settings.py	2014-02-25 17:45:25 +0000
@@ -1,4 +1,4 @@
-# Copyright (C) 2013 Canonical Ltd.
+# Copyright (C) 2013-2014 Canonical Ltd.
 # Author: Barry Warsaw <[e-mail]>
 
 # This program is free software: you can redistribute it and/or modify

=== modified file 'systemimage/tests/test_state.py'
--- systemimage/tests/test_state.py	2013-12-13 13:55:51 +0000
+++ systemimage/tests/test_state.py	2014-02-25 17:45:25 +0000
@@ -1,4 +1,4 @@
-# Copyright (C) 2013 Canonical Ltd.
+# Copyright (C) 2013-2014 Canonical Ltd.
 # Author: Barry Warsaw <[e-mail]>
 
 # This program is free software: you can redistribute it and/or modify

=== modified file 'systemimage/tests/test_winner.py'
--- systemimage/tests/test_winner.py	2013-12-13 13:55:51 +0000
+++ systemimage/tests/test_winner.py	2014-02-25 17:45:25 +0000
@@ -1,4 +1,4 @@
-# Copyright (C) 2013 Canonical Ltd.
+# Copyright (C) 2013-2014 Canonical Ltd.
 # Author: Barry Warsaw <[e-mail]>
 
 # This program is free software: you can redistribute it and/or modify

=== modified file 'systemimage/version.txt'
--- systemimage/version.txt	2013-12-13 13:55:51 +0000
+++ systemimage/version.txt	2014-02-25 17:45:25 +0000
@@ -1,1 +1,1 @@
-2.0.3
+2.1

=== modified file 'tox.ini'
--- tox.ini	2013-12-13 13:55:51 +0000
+++ tox.ini	2014-02-25 17:45:25 +0000
@@ -1,5 +1,5 @@
 [tox]
-envlist = py33
+envlist = py33, py34
 
 [testenv]
 commands = python -m nose2 -v