Added support for sound notification plugins which use

the desktop sound theme, with pycanberra for example. Plugin name should
start with 'theme' in that case, whereas the name of plugins playing the
sound file starts with 'file'.

setup.py

@@ -285,7 +285,8 @@ if __name__ == "__main__":
                     '[notify2]'
                 ],
                 'notification.sound': [
-                    'fallback = pybitmessage.plugins.sound_playfile [sound]'
+                    'file.fallback = pybitmessage.plugins.sound_playfile'
+                    '[sound]'
                 ],
                 # 'console_scripts': [
                 #        'pybitmessage = pybitmessage.bitmessagemain:main'

src/bitmessageqt/__init__.py

@@ -1387,6 +1387,7 @@ class MyForm(settingsmixin.SMainWindow):
             soundFilename = state.appdata + 'sounds/' + label
             ext = _choose_ext(soundFilename)
             if not ext:
+                category = self.SOUND_KNOWN
                 soundFilename = None
 
         if soundFilename is None:
@@ -1417,6 +1418,7 @@ class MyForm(settingsmixin.SMainWindow):
                 soundFilename = state.appdata + 'sounds/green'
 
         if soundFilename is None:
+            logger.warning("Probably wrong category number in playSound()")
             return
 
         if not self.isConnectionSound(category):
@@ -1428,7 +1430,10 @@ class MyForm(settingsmixin.SMainWindow):
         except (TypeError, NameError):
             ext = _choose_ext(soundFilename)
             if not ext:
-                return
+                try:  # if no user sound file found try to play from theme
+                    return self._theme_player(category, label)
+                except TypeError:
+                    return
 
             soundFilename += ext
 
@@ -1450,6 +1455,10 @@ class MyForm(settingsmixin.SMainWindow):
         _plugin = get_plugin('notification.message')
         if _plugin:
             self._notifier = _plugin
+        else:
+            logger.warning("No notification.message plugin found")
+
+        self._theme_player = get_plugin('notification.sound', 'theme')
 
         if not QtGui.QSound.isAvailable():
             _plugin = get_plugin(
@@ -1457,7 +1466,7 @@ class MyForm(settingsmixin.SMainWindow):
             if _plugin:
                 self._player = _plugin
             else:
-                logger.warning("No sound player plugin found!")
+                logger.warning("No notification.sound plugin found")
 
     def notifierShow(
             self, title, subtitle, category, label=None, icon=None):