Support for M4A audio files.

modules/scheduling/fallback_manager.py

@@ -226,7 +226,7 @@ class FallbackManager:
         Returns:
             (Boolean):      True, if it's an audio file.
         """
-        audio_extensions = [".wav", ".flac", ".mp3", ".ogg"]
+        audio_extensions = [".wav", ".flac", ".mp3", ".ogg", ".m4a"]
         ext = os.path.splitext(file)[1]
         abs_path = os.path.join(dir, file)