[BEAM-7218] Backport of #7487

[udim]

Also includes some fixes to Python precommit.

Test run: https://gradle.com/s/qlveilpllgxt4

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Post-Commit Tests Status (on master branch)

Lang	SDK	Apex	Dataflow	Flink	Gearpump	Samza	Spark
Go		---	---		---	---
Java
Python		---			---	---

Pre-Commit Tests Status (on master branch)

---	Java	Python	Go	Website
Non-portable
Portable	---		---	---

See .test-infra/jenkins/README for trigger phrase, status and link of all Jenkins jobs.

[udim]

ping, gradle scan of test run is in PR desc

[kennknowles]

It seems that neither stable nor latest are good choices for the pyhamcrest dep. Currently the tip of this branch cannot build docs, I am guessing because that version spec has changed.