Comment 10 for bug 1933109

It looks like the problem is that WSGI daemon processes have the default C locale.

https://www.gnu.org/software/libc/manual/html_node/Setting-the-Locale.html
"ISO C says that all programs start by default in the standard ‘C’ locale"

I think setting the lang variable on a WSGIDaemonProcess might help.
https://modwsgi.readthedocs.io/en/develop/configuration-directives/WSGIDaemonProcess.html#lang

I would give it a quick test to see if it helps and then we could possibly set it in the charm. If it fixes things, it might be reasonable to query /etc/default/locale or `localectl status` in the charm and set the `lang` option for all for `WSGIDaemonProcess`es.