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 rust-rspolib 's PO files:

gettext: tests-data/2-translated-entries.po: can't guess language
gettext: tests-data/comment-ordering.po: can't guess language
gettext: tests-data/django-complete.po: can't guess language
gettext: tests-data/empty-metadata.po: can't guess language
gettext: tests-data/empty-occurrences-line.po: can't guess language
gettext: tests-data/empty.po: can't guess language
gettext: tests-data/escapes.po: can't guess language
gettext: tests-data/flags.po: can't guess language
gettext: tests-data/fuzzy-header.po: can't guess language
gettext: tests-data/fuzzy-no-fuzzy.po: can't guess language
gettext: tests-data/header-no-trailing-newline.po: can't guess language
gettext: tests-data/header-trailing-newlines.po: can't guess language
gettext: tests-data/indented.po: can't guess language
gettext: tests-data/invalid-previous-msgid-continuation.po: can't guess language
gettext: tests-data/long-message.po: can't guess language
gettext: tests-data/metadata.po: can't guess language
gettext: tests-data/msgctxt.po: can't guess language
gettext: tests-data/msgid-msgstr-long.po: can't guess language
gettext: tests-data/msgid-msgstr.po: can't guess language
gettext: tests-data/msgid-plural.po: can't guess language
gettext: tests-data/msgids-msgstrs.po: can't guess language
gettext: tests-data/natural-unsorted-metadata.po: can't guess language
gettext: tests-data/obsolete-previous-msgid.po: can't guess language
gettext: tests-data/obsoletes.po: can't guess language
gettext: tests-data/occurrence-no-linenum.po: can't guess language
gettext: tests-data/previous-msgid-continuation.po: can't guess language
gettext: tests-data/previous-msgid-msgctxt.po: can't guess language
gettext: tests-data/repeated-metadata-keys.po: can't guess language
gettext: tests-data/unclosed-string-delimiter.po: can't guess language
gettext: tests-data/unescaped-double-quote-continuation.po: can't guess language
gettext: tests-data/unescaped-double-quote-msgid.po: can't guess language
gettext: tests-data/utf8-bom.po:1:2: syntax error
msgfmt: found 1 fatal error
gettext: tests-data/weird-occurrences.po: can't guess language
gettext: tests-data/wrapping.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.