Run localised unit tests
Tickets like #2164 (closed) highlight again that we have a test gap for localised environments.
See #2164 (closed)
Currenlty, afaik, the unit tests are only run in the the native language (en_US).
If there is an automated/easy way to do so, we should run the unit test suite in selected (or all?) localisations. Maybe not all the time (as in the PR hooks), but e.g. before a release.
I'm sure somebody has already looked into that, and I'd like to know what the main obstacles were.