Merge lp:~stub/charm-helpers/fix-systemd-detection into lp:charm-helpers

[Stuart Bishop]

Per Bug #1670944, trusty charms start failing if the snapd package
is installed on the system. Fix this.

I've just hardcoded the check for trusty, rather than some convoluted
method to attempt to detect if upstart is the default init system,
because we only need this to work under trusty. xenial is fine, and
systemd doesn't exist for precise.

[Stuart Bishop (stub)]

Note that having the snapd package installed is beyond the control of the charm, as it may be pulled in by a subordinate or layer.

[Chris MacNaughton (chris.macnaughton)]

Looks reasonable to me

review: Approve

[Tim Van Steenburgh (tvansteenburgh)]

+1

review: Approve

[James Page (james-page)]

review: Approve

=== modified file 'charmhelpers/core/host.py'
--- charmhelpers/core/host.py	2017-02-09 22:15:56 +0000
+++ charmhelpers/core/host.py	2017-03-08 06:59:35 +0000
@@ -306,6 +306,8 @@
 
 def init_is_systemd():
     """Return True if the host system uses systemd, False otherwise."""
+    if lsb_release()['DISTRIB_CODENAME'] == 'trusty':
+        return False
     return os.path.isdir(SYSTEMD_SYSTEM)
 
 
 
=== modified file 'tests/core/test_host.py'
--- tests/core/test_host.py	2017-02-09 22:15:56 +0000
+++ tests/core/test_host.py	2017-03-08 06:59:35 +0000
@@ -81,20 +81,34 @@
 
 class HelpersTest(TestCase):
 
+    @patch('charmhelpers.core.host.lsb_release')
     @patch('os.path')
-    def test_init_is_systemd_upstart(self, path):
+    def test_init_is_systemd_upstart(self, path, lsb_release):
         """Upstart based init is correctly detected"""
+        lsb_release.return_value = {'DISTRIB_CODENAME': 'whatever'}
         path.isdir.return_value = False
         self.assertFalse(host.init_is_systemd())
         path.isdir.assert_called_with('/run/systemd/system')
 
+    @patch('charmhelpers.core.host.lsb_release')
     @patch('os.path')
-    def test_init_is_systemd_system(self, path):
+    def test_init_is_systemd_system(self, path, lsb_release):
         """Systemd based init is correctly detected"""
+        lsb_release.return_value = {'DISTRIB_CODENAME': 'whatever'}
         path.isdir.return_value = True
         self.assertTrue(host.init_is_systemd())
         path.isdir.assert_called_with('/run/systemd/system')
 
+    @patch('charmhelpers.core.host.lsb_release')
+    @patch('os.path')
+    def test_init_is_systemd_trusty(self, path, lsb_release):
+        # Never returns true under trusty, even if the systemd
+        # packages have been installed. lp:1670944
+        lsb_release.return_value = {'DISTRIB_CODENAME': 'trusty'}
+        path.isdir.return_value = True
+        self.assertFalse(host.init_is_systemd())
+        self.assertFalse(path.isdir.called)
+
     @patch.object(host, 'init_is_systemd')
     @patch('subprocess.call')
     def test_runs_service_action(self, mock_call, systemd):