pyreadiness.org uses https://github.com/brettcannon/caniusepython3 to figure out if a project supported Python 3. The issue is that gevent doesn't specify their support through a trove classifier on PyPI. There is a hand curated overrides file, though, that I just edited to list as supported (https://github.com/brettcannon/caniusepython3/blob/master/ca...). I don't know how often py3readiness.org updates, but the issue should resolve itself the next time they update the data on the site.