I see supervisor is now happily supporting Python 3 but it still appears marked as _non-support_ to Python 3 on https://python3wos.appspot.com and http://py3readiness.org py3readiness.org mentions that it uses https://github.com/brettcannon/caniusepython3 to check availability of the package. We can see the online check for supervisor here: https://caniusepython3.com/project/supervisor I am not sure why the online checker says supervisor has _1 blocker_ for python 3 port.