pygrack: address webob AcceptValidHeader DeprecationWarning Got warnings like: kallithea/tests/other/test_vcs_operations.py::TestVCSOperations::test_yada_yada .../site-packages/webob/acceptparse.py:649: DeprecationWarning: The behavior of AcceptValidHeader.__contains__ is currently being maintained for backward compatibility, but it will change in the future to better conform to the RFC. DeprecationWarning, There *must* be a better alternative to pygrack ... for now, let's keep it alive.