Drop support of python 2 and make the code compatible with python 3 so that the add-on works on Kodi 19.
Update Kodistubs version in the CI and get rid of the python 2 actions.
Note: script.module.libtorrent is disabled because it will not be used on Matrix (and is not compatible).
It will be replaced by vfs.libtorrent[1] when ready.
[1]: https://framagit.org/thombet/vfs.libtorrent
The URL of the video is not stored in the same attribute of the response
if WebTorrent is enabled or not.
It caused a bug when trying to play a video which do not use WebTorrent.
Also create a "quality" job to run pylint automatically on merge
requests. The contributing guidelines are updated with this information
and the remaining pylint violations were fixed in the code.
See merge request StCyr/plugin.video.peertube!11 for more information
Thomas