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 doublecmd 's PO files:

gettext: language/doublecmd.fr.po: warning: Charset missing in header.
                                                                                    Message conversion to user's charset will not work.
language/doublecmd.fr.po:60:44: syntax error
language/doublecmd.fr.po:12305: keyword "Erreur" unknown
language/doublecmd.fr.po:12305:9: syntax error
language/doublecmd.fr.po:12306: end-of-line within string
msgfmt: found 4 fatal errors
gettext: language/lcl/lclstrconsts.pb.po: pb not a language code
gettext: plugins/wcx/zip/language/zip.be.po: zip not a language code
gettext: plugins/wcx/zip/language/zip.de.po: zip not a language code
gettext: plugins/wcx/zip/language/zip.hu.po: zip not a language code
gettext: plugins/wcx/zip/language/zip.ko.po: zip not a language code
gettext: plugins/wcx/zip/language/zip.po: zip not a language code
gettext: plugins/wcx/zip/language/zip.ru.po: zip not a language code
gettext: plugins/wcx/zip/language/zip.zh_CN.po: zip not a language code
gettext: plugins/wfx/ftp/language/ftp.be.po: ftp not a language code
gettext: plugins/wfx/ftp/language/ftp.de.po: ftp not a language code
gettext: plugins/wfx/ftp/language/ftp.hu.po: ftp not a language code
gettext: plugins/wfx/ftp/language/ftp.ko.po: ftp not a language code
gettext: plugins/wfx/ftp/language/ftp.ru.po: ftp not a language code
gettext: plugins/wfx/ftp/language/ftp.zh_CN.po: ftp not a language code
      

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.