Oops, we need to use defer.returnValue.

synapse/handlers/presence.py

@@ -142,7 +142,8 @@ class PresenceHandler(BaseHandler):
 
     @defer.inlineCallbacks
     def is_presence_visible(self, observer_user, observed_user):
-        return defer.succeed(True)
+        defer.returnValue(True)
+        return
         # FIXME (erikj): This code path absolutely kills the database.
 
         assert(observed_user.is_mine)