Check dict is not empty before acknowledging messages upon context exit. Closes googleapis#2878.

quom · quom · commit 9f917b97669b · 2016-12-16T10:48:49.000Z
diff --git a/pubsub/google/cloud/pubsub/subscription.py b/pubsub/google/cloud/pubsub/subscription.py
@@ -509,4 +509,5 @@ def __enter__(self):
         return self
 
     def __exit__(self, exc_type, exc_val, exc_tb):
-        self._subscription.acknowledge(list(self), self._client)
+        if self:
+            self._subscription.acknowledge(list(self), self._client)
