15110: set env var for subprocess, check version in script

[eevelweezel]

Fixes #15110

• Add PYTHONSAFEPATH="true" to call to subprocess in get_search_dirs()
• Check sys.version_info before modifying path in pyinfo.py

To test, import mypy.modulefinder.get_search_dirs & run:

• get_search_dirs() with no args
• on Python 3.11, call get_search_dirs with an earlier version as python_executable
• on Python < 3.11, call get_search_dirs with Python 3.11 as python_executable

Expected:

• consistent results, no exceptions

[hauntsaninja]

This looks great, thanks for the fix!

[hauntsaninja]

Fatal Python error: _Py_HashRandomization_Init: failed to get random numbers to initialize Python quite bizarre. The internet suggests that doing the equivalent of passing env={**os.environ, "PYTHONSAFEPATH": "1"} will work

[github-actions]

According to mypy_primer, this change has no effect on the checked open source code. 🤖🎉

[hauntsaninja]

Thanks again!