PR 235790

While I'm here:

• Sort variables a bit according to the PHB

Changelog:

• Switched from Python 2 to Python 3
• All changes since 1.5.5:

https://syncplay.pl/changelog/

• poudriere (11.2-, 12.0-RELEASE, 13.0-CURRENT@r344112 amd64 + i386) with options CLIENT and/or SERVER enabled and GUI and/or VLC enabled -> OK
• portlint -> OK (brings warnings about icon installation but this can be ignored because it's a Qt application that handles icons differently, AFAIK)
• Runtime test -> OK