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 paperwork 's PO files:

gettext: openpaperwork-core/l10n/zh_Hans.po: can't guess language
gettext: openpaperwork-gtk/l10n/zh_Hans.po: can't guess language
gettext: paperwork-backend/l10n/zh_Hans.po: can't guess language
gettext: paperwork-gtk/l10n/zh_Hans.po: can't guess language
gettext: paperwork-gtk/src/paperwork_gtk/model/help/data/l10n/zh_Hans.po: can't guess language
gettext: paperwork-shell/l10n/zh_Hans.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.