gh-121359: make clean environment (no PYTHON* vars) for test_pyrepl.TestMain

[skirpichev]

• Issue: gh-121359

[skirpichev]

I think this can skip news;)

[bedevere-app[bot]]

A Python core developer has requested some changes be made to your pull request before we can consider merging it. If you could please address their requests along with any other requests in other reviews from core developers that would be appreciated.

Once you have made the requested changes, please leave a comment on this pull request containing the phrase I have made the requested changes; please review again. I will then notify any core developers who have left a review that you're ready for them to take another look at this pull request.

[skirpichev]

I have made the requested changes; please review again

[bedevere-app[bot]]

Thanks for making the requested changes!

@pablogsal: please review the changes made to this pull request.

[smontanaro]

test_pyrepl passes after applying the PR to an up-to-date main branch.

[miss-islington-app[bot]]

Thanks @skirpichev for the PR, and @ambv for merging it 🌮🎉.. I'm working now to backport this PR to: 3.13. 🐍🍒⛏🤖

[bedevere-app[bot]]

GH-121810 is a backport of this pull request to the 3.13 branch.