Fix locales format based on wrong assumption
Originally created by Tails on #6001 (Redmine)
A few places in Tails (
git grep LANG) assume everything that can be in
$LANG starts with the
xx_XX form, which is, unfortunately, not true:
Instead of relying home-made shell trickery and re-inventing the wheel we should consider using some existing library or tool for this, or we should read the standards so we can prevent buggy edge cases.