Fix typo when getting app name

synapse/push/pusher.py

@@ -58,7 +58,7 @@ class PusherFactory(object):
             return self.pusher_types[pusherdict['kind']](self.hs, pusherdict)
 
     def _create_email_pusher(self, _hs, pusherdict):
-        app_name = self._brand_from_pusherdict
+        app_name = self._app_name_from_pusherdict(pusherdict)
         mailer = self.mailers.get(app_name)
         if not mailer:
             mailer = Mailer(