_get_default_service_project_id() fails in appveyor

[daspecster]

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FAIL: test_read_from_cli_info (gcloud.test__helpers.Test__get_default_service_project_id)
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Traceback (most recent call last):
  File "C:\projects\gcloud-python\gcloud\test__helpers.py", line 223, in test_read_from_cli_info
    self.assertEqual('test-project-id', project_id)
AssertionError: 'test-project-id' != None

See also #1973