tests/test_versions.py:7
/home/travis/build/readthedocs/readthedocs-docker-images/tests/test_versions.py:7: PytestUnknownMarkWarning: Unknown pytest.mark.image_master - is this a typo? You can register custom marks to avoid this warning - for details, see https://docs.pytest.org/en/stable/mark.html
@pytest.mark.image_master
This is to avoid a WARNING,