The Python release process runs tests sequentially. It catchs some issues which are ignored silently when running tests in parallel.

I propose adding --sequentially option to regrtest to always run tests sequentially. It can be used to ignore any -jN option and also to re-run failed tests sequentially.

Linked PRs

• gh-119727: Add --single-process option to regrtest #119728
• gh-119727: Run tests in parallel by default #120456
• [3.13] gh-119727: Add --single-process option to regrtest (#119728) #123010
• [3.12] gh-119727: Add --single-process option to regrtest (GH-119728) #130359