Make sure bad data to OUTPUT does not deadlock.

- Moves GStreamer initialization out of on-start as it is not obvious to me how
  to stop rest of setup on other ways.

- Note that gst.GError != gobject.GError as far as except is concerned.

mopidy/core.py

@@ -20,7 +20,7 @@ sys.argv[1:] = gstreamer_args
 
 from mopidy import (get_version, settings, OptionalDependencyError,
     SettingsError, DATA_PATH, SETTINGS_PATH, SETTINGS_FILE)
-from mopidy.gstreamer import GStreamer
+from mopidy.gstreamer import GStreamer, GStreamerError
 from mopidy.utils import get_class
 from mopidy.utils.log import setup_logging
 from mopidy.utils.path import get_or_create_folder, get_or_create_file
@@ -45,6 +45,8 @@ def main():
         loop.run()
     except SettingsError as e:
         logger.error(e.message)
+    except GStreamerError as e:
+        logger.error(e)
     except KeyboardInterrupt:
         logger.info(u'Interrupted. Exiting...')
     except Exception as e:

mopidy/gstreamer.py

@@ -1,5 +1,6 @@
 import pygst
 pygst.require('0.10')
+import gobject
 import gst
 
 import logging
@@ -13,6 +14,10 @@ from mopidy.backends.base import Backend
 logger = logging.getLogger('mopidy.gstreamer')
 
 
+class GStreamerError(Exception):
+    pass
+
+
 class GStreamer(ThreadingActor):
     """
     Audio output through `GStreamer <http://gstreamer.freedesktop.org/>`_.
@@ -39,7 +44,6 @@ class GStreamer(ThreadingActor):
         self._volume = None
         self._output = None
 
-    def on_start(self):
         self._setup_pipeline()
         self._setup_output()
         self._setup_message_processor()
@@ -61,7 +65,12 @@ class GStreamer(ThreadingActor):
             self._pipeline.get_by_name('convert').get_pad('sink'))
 
     def _setup_output(self):
-        self._output = gst.parse_bin_from_description(settings.OUTPUT, True)
+        try:
+            self._output = gst.parse_bin_from_description(settings.OUTPUT, True)
+        except gobject.GError as e:
+            raise GStreamerError('%r while creating %r' % (e.message,
+                                                           settings.OUTPUT))
+
         self._pipeline.add(self._output)
         gst.element_link_many(self._volume, self._output)
         logger.debug('Output set to %s', settings.OUTPUT)

tests/gstreamer_test.py

@@ -14,7 +14,6 @@ class GStreamerTest(unittest.TestCase):
         settings.BACKENDS = ('mopidy.backends.local.LocalBackend',)
         self.song_uri = path_to_uri(path_to_data_dir('song1.wav'))
         self.gstreamer = GStreamer()
-        self.gstreamer.on_start()
 
     def prepare_uri(self, uri):
         self.gstreamer.prepare_change()
@@ -71,3 +70,8 @@ class GStreamerTest(unittest.TestCase):
     @unittest.SkipTest
     def test_set_position(self):
         pass # TODO
+
+    @unittest.SkipTest
+    def test_invalid_output_raises_error(self):
+        pass # TODO
+