bpo-42944 Fix Random.sample when counts is not None

[jonanifranco]

Use the instance generator instead of the module generator.

https://bugs.python.org/issue42944

[the-knights-who-say-ni]

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[rhettinger]

• Please sign the contributor agreement (CLA).
• Add a test that fails before the PR and passes afterward.
• Add a Misc/NEWS entry using Blurb.

[serhiy-storchaka]

Interesting, that there is a test which should catch this bug, but it does not work because it tests only global random.sample().

Please replace random with self.gen in test_sample_counts_equivalence and move that method to MersenneTwister_TestBasicOps, because it does not make sense for SystemRandom.

[jonanifranco]

I had just updated my master branch with a new test before reading @serhiy-storchaka comment. I update again test_random.py as suggested.

[rhettinger]

Please add an entry to Misc/NEWS.

[jonanifranco]

Please add an entry to Misc/NEWS.

Done.
I also signed the CLA yesterday.

[miss-islington]

Thanks @jonanifranco for the PR, and @rhettinger for merging it 🌮🎉.. I'm working now to backport this PR to: 3.9.
🐍🍒⛏🤖

[bedevere-bot]

GH-24243 is a backport of this pull request to the 3.9 branch.