unsupportedpastels M5: both hooks ran whatever python3 came first on PATH, but
scripts/check imports ruff_runner, which imports tomllib (3.11+, the project
minimum). With Ubuntu 22.04's python3 3.10 every hooked commit or push died with
"ModuleNotFoundError: No module named 'tomllib'".
The hooks now use the repo's virtualenv interpreter when there is one (.venv/ or
venv/, bin/python or Scripts/python.exe; this worktree first, then the main
checkout) and fall back to python3, then python. scripts/check checks
sys.version_info before importing the engine and exits 2 with a one-line message
naming the virtualenv instead of a traceback. Verified with a real CPython 3.10.21:
exit 2 and the message, where 96bb97a crashed in ruff_runner.
f472161acb