listener: Kill off mopidy.listener.send_async

This is no longer needed as the plain send method makes sure to use tell to
queue actor message. Which has better performance, and avoids deadlocks.

A side effect of this is that assuming you have a core actor running and a
dummy audio in use audio events just work.

mopidy/audio/listener.py

@@ -18,7 +18,7 @@ class AudioListener(listener.Listener):
     @staticmethod
     def send(event, **kwargs):
         """Helper to allow calling of audio listener events"""
-        listener.send_async(AudioListener, event, **kwargs)
+        listener.send(AudioListener, event, **kwargs)
 
     def reached_end_of_stream(self):
         """

mopidy/backend.py

@@ -426,7 +426,7 @@ class BackendListener(listener.Listener):
     @staticmethod
     def send(event, **kwargs):
         """Helper to allow calling of backend listener events"""
-        listener.send_async(BackendListener, event, **kwargs)
+        listener.send(BackendListener, event, **kwargs)
 
     def playlists_loaded(self):
         """

mopidy/core/listener.py

@@ -18,7 +18,7 @@ class CoreListener(listener.Listener):
     @staticmethod
     def send(event, **kwargs):
         """Helper to allow calling of core listener events"""
-        listener.send_async(CoreListener, event, **kwargs)
+        listener.send(CoreListener, event, **kwargs)
 
     def on_event(self, event, **kwargs):
         """

mopidy/listener.py

@@ -7,16 +7,6 @@ import pykka
 logger = logging.getLogger(__name__)
 
 
-def send_async(cls, event, **kwargs):
-    # This file is imported by mopidy.backends, which again is imported by all
-    # backend extensions. By importing modules that are not easily installable
-    # close to their use, we make some extensions able to run their tests in a
-    # virtualenv with global site-packages disabled.
-    import gobject
-
-    gobject.idle_add(lambda: send(cls, event, **kwargs))
-
-
 def send(cls, event, **kwargs):
     listeners = pykka.ActorRegistry.get_by_class(cls)
     logger.debug('Sending %s to %s: %s', event, cls.__name__, kwargs)

mopidy/mixer.py

@@ -130,7 +130,7 @@ class MixerListener(listener.Listener):
     @staticmethod
     def send(event, **kwargs):
         """Helper to allow calling of mixer listener events"""
-        listener.send_async(MixerListener, event, **kwargs)
+        listener.send(MixerListener, event, **kwargs)
 
     def volume_changed(self, volume):
         """