Better cleanup PYTHONPATH for Mercurial calls (support for PDM)

[paugier]

PDM uses the same strategy as pip for the build isolation except that the path of the temporary directory starts with "pdm-build-env-" and not "pip-build-env-".

Therefore, Mercurial (a Python application) installations can be broken and we need to clean up PYTHONPATH from such paths.

[RonnyPfannschmidt]

i wonder if there is a good integration test for this

[paugier]

I don't think there is a specific test about this mechanism. However, setuptools_scm._run_cmd.run is executed during the tests. I guess that setuptools_scm is tested with an installation with pip. If it is the case, this line is covered.

A problem is that pep 517 does not specify how the frontends implement the isolated build (https://peps.python.org/pep-0517/#build-environment), so we can just try to avoid known issues.

[paugier]

Thanks @RonnyPfannschmidt. Do you think a new version could be released on PyPI? I see that the last version was released on May 2024.

[RonnyPfannschmidt]

I'll try, but no promises, I'm suffering a stomach infection

[paugier]

Oh I hope you will recover soon. Be brave.

I'm working on modernizing Mercurial setup.py and I'd like to try to use setuptools-scm. But of course your health is more important than open-source!

Beside, do not hesitate to tell me if I can help on anything for setuptools-scm.