If timeout=0, return immediately

synapse/notifier.py

@@ -178,9 +178,13 @@ class Notifier(object):
         if timeout:
             reactor.callLater(timeout/1000, self._timeout_listener, listener)
 
-        self._register_with_keys(listener)
+            self._register_with_keys(listener)
+
         yield self._check_for_updates(listener)
 
+        if not timeout:
+            self._timeout_listener(listener)
+
         return
 
     def _timeout_listener(self, listener):