ADD only_if_coordinator decorator to sonos

Currently we interact with players regardless of thir coordinator
role, hence soco.exceptions.SoCoSlaveException are thrown. The use
of the decorator for each interactive method should address this

homeassistant/components/media_player/sonos.py

@@ -66,6 +66,26 @@ def setup_platform(hass, config, add_devices, discovery_info=None):
     return True
 
 
+def only_if_coordinator(func):
+    """
+    If used as decorator, avoid calling the decorated method if
+    player is not a coordinator.
+    If not, a grouped speaker (not in coordinator role)
+    will throw soco.exceptions.SoCoSlaveException
+    """
+
+    def wrapper(*args, **kwargs):
+        """ Decorator wrapper """
+        if args[0].is_coordinator:
+            return func(*args, **kwargs)
+        else:
+            _LOGGER.debug('Ignore command "%s" for Sonos device "%s" '
+                          '(not coordinator)',
+                          func.__name__, args[0].name)
+
+    return wrapper
+
+
 # pylint: disable=too-many-instance-attributes, too-many-public-methods
 # pylint: disable=abstract-method
 class SonosDevice(MediaPlayerDevice):
@@ -107,6 +127,11 @@ class SonosDevice(MediaPlayerDevice):
             return STATE_IDLE
         return STATE_UNKNOWN
 
+    @property
+    def is_coordinator(self):
+        """ Returns true if player is a coordinator """
+        return self._player.is_coordinator
+
     def update(self):
         """ Retrieve latest state. """
         self._name = self._player.get_speaker_info()['zone_name'].replace(
@@ -170,46 +195,57 @@ class SonosDevice(MediaPlayerDevice):
         """ Flags of media commands that are supported. """
         return SUPPORT_SONOS
 
+    @only_if_coordinator
     def turn_off(self):
         """ Turn off media player. """
         self._player.pause()
 
+    @only_if_coordinator
     def volume_up(self):
         """ Volume up media player. """
         self._player.volume += 1
 
+    @only_if_coordinator
     def volume_down(self):
         """ Volume down media player. """
         self._player.volume -= 1
 
+    @only_if_coordinator
     def set_volume_level(self, volume):
         """ Set volume level, range 0..1. """
         self._player.volume = str(int(volume * 100))
 
+    @only_if_coordinator
     def mute_volume(self, mute):
         """ Mute (true) or unmute (false) media player. """
         self._player.mute = mute
 
+    @only_if_coordinator
     def media_play(self):
         """ Send paly command. """
         self._player.play()
 
+    @only_if_coordinator
     def media_pause(self):
         """ Send pause command. """
         self._player.pause()
 
+    @only_if_coordinator
     def media_next_track(self):
         """ Send next track command. """
         self._player.next()
 
+    @only_if_coordinator
     def media_previous_track(self):
         """ Send next track command. """
         self._player.previous()
 
+    @only_if_coordinator
     def media_seek(self, position):
         """ Send seek command. """
         self._player.seek(str(datetime.timedelta(seconds=int(position))))
 
+    @only_if_coordinator
     def turn_on(self):
         """ Turn the media player on. """
         self._player.play()