Fix bug where we used an unbound local variable if we ended up rolling back the persist_event transaction

synapse/storage/__init__.py

@@ -77,7 +77,7 @@ class DataStore(RoomMemberStore, RoomStore,
             stream_ordering = self.min_token
 
         try:
-            latest = yield self._db_pool.runInteraction(
+            yield self._db_pool.runInteraction(
                 self._persist_pdu_event_txn,
                 pdu=pdu,
                 event=event,
@@ -86,7 +86,6 @@ class DataStore(RoomMemberStore, RoomStore,
             )
         except _RollbackButIsFineException as e:
             pass
-        defer.returnValue(latest)
 
     @defer.inlineCallbacks
     def get_event(self, event_id, allow_none=False):
@@ -214,8 +213,6 @@ class DataStore(RoomMemberStore, RoomStore,
                 }
             )
 
-        return self._get_room_events_max_id_txn(txn)
-
     @defer.inlineCallbacks
     def get_current_state(self, room_id, event_type=None, state_key=""):
         sql = (