Unable to continue using custom languages with Django

[Barney Szabolcs]

with gettext version 0.22.5, Somali (so) and Cantonese (yue) stopped working.
If I remove language files for these two languages, the runserver works fine,
if I add back these two languages, error: ValueError: invalid token in plural form: EXPRESSION

Also, makemessages CommandError: Type 'manage.py help makemessages' for usage information.

Whereas, if I run makemessages -l so -l yue it works fine, but still the project does not start, yielding the same error.
What's even weirder: if I set makemessages -x de (that should be irrelevant), then makemessages runs also fine.
Compilemessages runs also just fine.

This is a weird regression. Tested with python 3.9, 3.11, 3.12, all the same, Django 3.2.19, 4.2.11, 5.0.2.

Quick fix: if needed, I can generate a quick translation for the Django .po files, using ChatGPT, but I don't know anyone who speaks Somali or Cantonese.