fix: Prevent NameError when accessing _DISTUTILS_PATCH during file ov…

[gracetyy]

Fixes #2969.

• ran the linter to address style issues (tox -e fix)
• wrote descriptive pull request text
• ensured there are test(s) validating the fix
• added news fragment in docs/changelog folder
• updated/extended the documentation (not required for this bugfix)

Problem

Race condition in _virtualenv.py causes NameError: name '_DISTUTILS_PATCH' is not defined when the file is being overwritten (e.g., by uv venv --allow-existing) while another process is using it (e.g., marimo notebook).

Solution

Added defensive try-except NameError blocks around _DISTUTILS_PATCH and patch_dist references in _Finder.find_spec(), _Finder.exec_module(), and _Finder.load_module() methods to handle the race condition.

[gracetyy]

Sorry for all the issues in the previous commit! I've addressed all your feedback and thank you for your time.

[gracetyy]

Thanks