Merge lp:~gandelman-a/charm-helpers/loopback_fix into lp:charm-helpers

[Adam Gandelman]

contrib.storage.linux.loopback: Fix create_loopback() to actually return full path of new device.

create_loopback() is expected to return the full path of a newly created loopback. 'losetup --find' does not return any output on creation, so inspect loopback_devices() after creation and actually return path.

=== modified file 'charmhelpers/contrib/storage/linux/loopback.py'
--- charmhelpers/contrib/storage/linux/loopback.py	2013-06-24 22:39:29 +0000
+++ charmhelpers/contrib/storage/linux/loopback.py	2013-07-19 00:23:39 +0000
@@ -35,8 +35,11 @@
 
     :returns: str: Full path to new loopback device (eg, /dev/loop0)
     '''
-    cmd = ['losetup', '--find', file_path]
-    return check_output(cmd).strip()
+    file_path = os.path.abspath(file_path)
+    check_call(['losetup', '--find', file_path])
+    for d, f in loopback_devices().iteritems():
+        if f == file_path:
+            return d
 
 
 def ensure_loopback_device(path, size):

=== modified file 'tests/contrib/storage/test_linux_storage_loopback.py'
--- tests/contrib/storage/test_linux_storage_loopback.py	2013-06-24 22:39:29 +0000
+++ tests/contrib/storage/test_linux_storage_loopback.py	2013-07-19 00:23:39 +0000
@@ -64,10 +64,12 @@
             check_call.assert_called_with(['truncate', '--size', '15G',
                                            '/tmp/foo.img'])
 
-    def test_create_loopback(self):
+    @patch.object(loopback, 'loopback_devices')
+    def test_create_loopback(self, _devs):
         '''It corectly calls losetup to create a loopback device'''
-        with patch(STORAGE_LINUX_LOOPBACK + '.check_output') as check_output:
-            check_output.return_value = '/dev/loop0'
+        _devs.return_value = {'/dev/loop0': '/tmp/foo'}
+        with patch(STORAGE_LINUX_LOOPBACK + '.check_call') as check_call:
+            check_call.return_value = ''
             result = loopback.create_loopback('/tmp/foo')
-            check_output.assert_called_with(['losetup', '--find', '/tmp/foo'])
+            check_call.assert_called_with(['losetup', '--find', '/tmp/foo'])
             self.assertEquals(result, '/dev/loop0')