container_registry.TestContainerAnalysisSamples.test_pubsub fails

[tmatsuo]

https://source.cloud.google.com/results/invocations/d992dc60-7879-4d9b-b958-1fd9070805d0/targets/github%2Fpython-docs-samples%2Fcontainer_registry%2Fcontainer_analysis/tests

Traceback (most recent call last):
  File "/tmpfs/src/github/python-docs-samples/container_registry/container_analysis/samples_test.py", line 165, in test_pubsub
    assert receiver.msg_count == total_created
AssertionError: assert 1 == 3
  -1
  +3

[tmatsuo]

I think it's a dup of #2894