The Python tests job is flaky

[github-actions]

The Python tests is failing over 50% of the time.
Please visit https://github.com/apache/beam/actions/workflows/python_tests.yml?query=is%3Afailure+branch%3Amaster to see all failed workflow runs.
See also Grafana statistics: http://metrics.beam.apache.org/d/CTYdoxP4z/ga-post-commits-status?orgId=1&viewPanel=7&var-Workflow=Python tests

[github-actions]

Reopening since the workflow is still flaky

[liferoad]

Last 10 runs look good.