Avoid mutate-while-iterating error under Py3k.

tseaver · tseaver · commit 982acdf8f20b · 2016-07-14T10:50:47.000-04:00
Addresses: googleapis#1636 (comment)
diff --git a/docs/pubsub_snippets.py b/docs/pubsub_snippets.py
@@ -378,7 +378,7 @@ def do_something_with(message):  # pylint: disable=unused-argument
     # [START subscription_pull_autoack]
     from gcloud.pubsub.subscription import AutoAck
     with AutoAck(subscription, max_messages=10) as ack:
-        for ack_id, message in ack.items():
+        for ack_id, message in list(ack.items()):
             try:
                 do_something_with(message)
             except Exception:  # pylint: disable=broad-except
