fix unsubscribe

Author: Tony Crisci

i3ipc/i3ipc.py

@@ -272,7 +272,7 @@ def subscribe(self, detailed_event, handler):
                                     'handler': handler})
 
     def unsubscribe(self, handler):
-        self._subscriptions = list(filter(lambda s: s['handler'] is handler, self._subscriptions))
+        self._subscriptions = list(filter(lambda s: s['handler'] != handler, self._subscriptions))
 
     def emit(self, event, data):
         detail = ''