Initial python3 changes

Mostly just updating libraries, removing string encoding/decoding,
fixing some edge cases. No new functionality was added in this
commit.

lib/beetsplug/sonosupdate.py

@@ -0,0 +1,46 @@
+# This file is part of beets.
+# Copyright 2018, Tobias Sauerwein.
+#
+# Permission is hereby granted, free of charge, to any person obtaining
+# a copy of this software and associated documentation files (the
+# "Software"), to deal in the Software without restriction, including
+# without limitation the rights to use, copy, modify, merge, publish,
+# distribute, sublicense, and/or sell copies of the Software, and to
+# permit persons to whom the Software is furnished to do so, subject to
+# the following conditions:
+#
+# The above copyright notice and this permission notice shall be
+# included in all copies or substantial portions of the Software.
+
+"""Updates a Sonos library whenever the beets library is changed.
+This is based on the Kodi Update plugin.
+"""
+
+from beets.plugins import BeetsPlugin
+import soco
+
+
+class SonosUpdate(BeetsPlugin):
+    def __init__(self):
+        super().__init__()
+        self.register_listener('database_change', self.listen_for_db_change)
+
+    def listen_for_db_change(self, lib, model):
+        """Listens for beets db change and register the update"""
+        self.register_listener('cli_exit', self.update)
+
+    def update(self, lib):
+        """When the client exists try to send refresh request to a Sonos
+        controler.
+        """
+        self._log.info('Requesting a Sonos library update...')
+
+        device = soco.discovery.any_soco()
+
+        if device:
+            device.music_library.start_library_update()
+        else:
+            self._log.warning('Could not find a Sonos device.')
+            return
+
+        self._log.info('Sonos update triggered')