Show an error instead of creating non-working env

[gdubicki]

for Python 2 on Apple Silicon (M1) Macs.

Related to #2024.

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• ran the linter to address style issues (tox -e fix_lint)
• wrote descriptive pull request text
• ensured there are test(s) validating the fix
• added news fragment in docs/changelog folder
• updated/extended the documentation

[gdubicki]

I cannot add a real test that would run on GitHub Actions as it doesn't provide Macs on Apple Silicon (yet).

But this code successfully fails ;P on my machine:

(venv) gdubicki@mac ~/git/virtualenv 2024_friendly_error $ .tox/dev/bin/virtualenv -p python2 venv4
Creating virtualenv for Python 2 on Apple Silicon Macs is not supported as of now.
RuntimeError: No virtualenv implementation for PathPythonInfo(spec=CPython2.7.16.final.0-64, system=/System/Library/Frameworks/Python.framework/Versions/2.7/Resources/Python.app/Contents/MacOS/Python, exe=/usr/bin/python2, platform=darwin, version='2.7.16 (default, Jun 18 2021, 03:23:52) \n[GCC Apple LLVM 12.0.5 (clang-1205.0.19.59.6) [+internal-os, ptrauth-isa=deploy', encoding_fs_io=utf-8-None)

[gaborbernat]

You'll need to remove this, as this would still print if someone adds support via a plugin

[gdubicki]

Thanks for a review @gaborbernat !

Unfortunately I am not familiar with this project's structure yet. Can you recommend a better place to put this check then?

Alternatively we could change this to:

logging.warning("The built-in creator does not handle creating virtualenvs for Python 2 on Apple Silicon Macs as of now.")

- that should not be misleading for a person that adds their own plugin to support this case.

[gaborbernat]

The location is good. There isn't a place to put the warning message though, so that needs to be removed just.

[gdubicki]

I am afraid that without this message this PR doesn't make sense as the whole point was to show a friendly error that explains what happened.

If I would get the generic "No virtualenv implementation" error then I would assume that something is wrong with my Python / virtualenv setup, not that it is actually a missing virtualenv feature. And I think that other users would do the same.

Maybe it would be easier for you to implement the missing plugin instead? I would love to do it myself but I just don't know enough about Mach-O hacking for it to make sense... I am willing to do all the testing you need and as it seems that we are in similar timezones (BST / CEST) we could sync easily.

[gaborbernat]

I would love to do it myself but I just don't know enough about Mach-O hacking to it to make sense

Me neither... And I don't have access to an Apple M1 machine to write an implementation for it or time to do that. So guess we wait until someone comes along who does.

[gdubicki]

On second thought it is better to fail with a proper error message than creating a non-working env, so I created #2189.