Merge a stricter version of check_po whose expectations are realistic into our master branch
It’s not clear if we really need #15362 (closed) nor whether it’s 100% realistic. So as a first step, before we can do sysadmin#15082 (closed), let’s merge the new version of this script, after reviewing its requirements, and disabling the new checks that cannot be easily satisfied at the moment: for example, checks that would not pass on PO files generated by current ikiwiki shall be disabled, at least for now.
Feature Branch: tails.git:translation_platform_hooks
Parent Task: #15079 (closed)