Python PostCommit failures

[Yifan Zou]

We are seeing consecutive Python PostCommit
<https://builds.apache.org/view/A-D/view/Beam/job/beam_PostCommit_Python_Verify/>
failures due to a broken IT test. I am looking into it (BEAM-5643
<https://issues.apache.org/jira/browse/BEAM-5643>).

Yifan