Today, we merged jumbo PR664: initial port to Python 3.
Together with previous merges (PyQt5), those are first steps to Picard 2.x
Adventurous people may start to test the master branch (dev only, no package yet).
Current requirements are listed in the updated INSTALL.md file, basically Python 3.5, PyQt5.7.1, mutagen 1.37.
Plugins aren't working yet, since we need to update Picard plugins web service and deploy Py3-compatible versions of the current plugins, this will be done within next days as PRs are mostly ready.
The main author to credit is @samj1912, of course, with the help of Mineo, Lazka, bitmap, Sophist, Zas, plus few others
A lot of code changed, so expect issues, please report them.