You can check if a PO file is valid with the following command:

        msgfmt -c -o /dev/null <po file>
      

The following errors were found in luanti 's PO files:

gettext: games/devtest/mods/testtranslations/locale/translation_po.fr.po: po not a language code
gettext: games/devtest/mods/testtranslations/test_locale/translation_po.de.po: po not a language code
gettext: games/devtest/mods/testtranslations/translation_mo.de.po: mo not a language code
gettext: games/devtest/mods/testtranslations/translation_mo.fr.po: mo not a language code
gettext: po/ms_Arab/luanti.po: can't guess language
gettext: po/sr_Cyrl/luanti.po: can't guess language
gettext: po/sr_Latn/luanti.po: can't guess language
      

Please ask the translator (identified by the Last-Translator field in the PO file), the language team (identified by the Language-Team field) or debian-i18n for a fix.