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 gettext-ant-tasks 's PO files:

gettext: src/test/resources/org/xnap/commons/ant/gettext/de-with-warnings.po: can't guess language
gettext: src/test/resources/org/xnap/commons/ant/gettext/fullytranslated.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.