The `pology` library runs on Python2 and development appears stalled. It
is also not available on pip.
The `babel` library, BSD-licensed, provides, amongst many other things,
a replacement for .POT / .PO manipulation.
The `poediff` tool that we used to detect spurious i18n change is
replaced with a Python script that does a simpler but good enough job
(it is also much, much faster).
These replacements let the i18n scripts run on Python3 entirely.
Makes D506 redundant.
Comments by: Itms
Reviewed By: Gallaecio
Refs #5694
Differential Revision: https://code.wildfiregames.com/D2757
This was SVN commit r24313.
