It says the information is from PyPI, and gunicorn is in the "Python 3" category on PyPI. That might be it. Edit: aha, that's probably the case. At the bottom

It says the information is from PyPI, and gunicorn is in the "Python 3" category on PyPI. That might be it. Edit: aha, that's probably the case. At the bottom of the page, it says: > If a module is red though it supports python 3 it's because they don't have the "Programming Language :: Python :: 3" tag.