[mahaase]

Installing packages into the system interpreter with python -m pip install fails on runner images that enforce PEP 668:

Run python -m pip install pre-commit
error: externally-managed-environment
× This environment is externally managed
╰─> To install Python packages system-wide, try apt install
    python3-xyz, where xyz is the package you are trying to
    install.
    
    If you wish to install a non-Debian-packaged Python package,
    create a virtual environment using python3 -m venv path/to/venv.
    Then use path/to/venv/bin/python and path/to/venv/bin/pip. Make
    sure you have python3-full installed.
    
    If you wish to install a non-Debian packaged Python application,
    it may be easiest to use pipx install xyz, which will manage a
    virtual environment for you. Make sure you have pipx installed.
    
    See /usr/share/doc/python3.12/README.venv for more information.

note: If you believe this is a mistake, please contact your Python installation or OS distribution provider. You can override this, at the risk of breaking your Python installation or OS, by passing --break-system-packages.
hint: See PEP 668 for the detailed specification.
Error: Process completed with exit code 1.

This is the case for Gitea Actions with the default gitea/runner-images:ubuntu-latest image (Ubuntu 24.04, Python 3.12). GitHub hosted runners still work because they ship a separately installed Python that is not marked as externally managed.

Create a virtualenv in $RUNNER_TEMP instead and put it into $GITHUB_PATH so that the following steps find the installed tools. This works the same on GitHub and Gitea and does not rely on the Python setup of the runner image.

Same like BobBuildTool/basement#338