I am skeptical of the link entirely. It says gevent does not support Python 3, yet if you look at the PyPI page [0], it says "Gevent runs on Python >= 2.6, Python >= 3.3, or PyPy >= 4.0.1 (but not PyPy3)". Is the lack of PyPy3 really worth saying Gevent doesn't run on Python 3 (the language, not CPython specifically)? Perhaps this website is out-of-date in some respects, and helps contribute to the confusion.
On an unrelated note, a lot of people I have encountered claim Gevent as the reason they haven't switched yet. For now I guess such claims are shaky, assuming the PyPI page isn't false advertising.
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.
This is actually very informative. Combined with mangeletti's answer, it does explain the discrepancy. Thank you for sharing this. It's interesting (and also sad) that this tool has evolved up to version 3.3.0 over the years since we had Python 3.0.
Their PyPI page explicitly says otherwise: https://pypi.python.org/pypi/supervisor . It looks like there is support in their repository but not in any official release (yet).
I found it shocking that Fabric was still not supported.