Python 3 support graph for 360 most popular Python packages!
This site shows Python 3 support for 360 most downloaded packages on PyPI
There can be many reasons a package is still not supporting Python 3.
If you are package maintainer, it's time to start porting (if you haven't already). Here is an in-depth guide Porting to Python 3 and blog post. If you are not able to give time needed, please seek for help from community by announcing on blog, IRC, mailing lists etc.
If you are user of the package, send friendly note to package maintainer. Or fork it, and send pull request.
This site utilizes little tool, caniusepython3 created by Brett Cannon. Throw your requirements.txt file at it and it will tell you which packages support Python 3, and list out which don't.