Pubsub system test: test_fetch_delete_subscription_w_deleted_topic does not see orphan w/o topic

[tseaver]

From: https://travis-ci.org/GoogleCloudPlatform/gcloud-python/builds/151011241#L822

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FAIL: test_fetch_delete_subscription_w_deleted_topic (pubsub.TestPubsub)
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Traceback (most recent call last):
  File "/home/travis/build/GoogleCloudPlatform/gcloud-python/system_tests/pubsub.py", line 273, in test_fetch_delete_subscription_w_deleted_topic
    self.assertTrue(orphaned.topic is None)
AssertionError: False is not true
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[dhermes]

@tseaver I just created the flaky label

[tseaver]

Again yesterday.

[tseaver]

Still failing on one of two runs after the merge of #2086.

[tseaver]

W00t! We have two passing post-merge builds after the merge of #2106:

• https://travis-ci.org/GoogleCloudPlatform/gcloud-python/builds/153004550
• https://travis-ci.org/GoogleCloudPlatform/gcloud-python/builds/153028304

[dhermes]

w00t!

[tseaver]

Ugh

[tseaver]

@tmatsuo Has there been some recently-deployed change to the Pubsub API which would cause this failure to go from "flaky" to "fails routinely"? Our current backoff ends up polling for four minutes, trying to get the deleted-topic response after deleting our "orphan" subscription's topic.

@dhermes, @daspecster If @tmatsuo doesn't know / suspect any back-end change which would explain the failures, I propose we drop this particular testcase: we have unittests in place which cover the oddball case, and we need to have our build stay green.