flake8:
    image: python:latest
    stage: code_quality
    script:
        - python --version  # Debug
        - python -m venv venv --upgrade-deps || python -m venv venv  # upgrade-deps is not supported before 3.9
        - source venv/bin/activate
        - pip install flake8
        - flake8
    only:
        changes:
            - ./**/*.py
            - .gitlab-ci.yml
            - pyproject.toml