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 gaphor 's PO files:

source does not specify a priority
gettext: docs/locale/zh_Hans/LC_MESSAGES/docs.po: can't guess language
gettext: po/ca.po:3540: duplicate message definition...
po/ca.po:950: ...this is the location of the first definition
po/ca.po:3543: duplicate message definition...
po/ca.po:955: ...this is the location of the first definition
po/ca.po:3546: duplicate message definition...
po/ca.po:2850: ...this is the location of the first definition
po/ca.po:3558: duplicate message definition...
po/ca.po:3062: ...this is the location of the first definition
msgfmt: found 4 fatal errors
gettext: po/cs.po:3587: duplicate message definition...
po/cs.po:920: ...this is the location of the first definition
po/cs.po:3590: duplicate message definition...
po/cs.po:925: ...this is the location of the first definition
po/cs.po:3593: duplicate message definition...
po/cs.po:2868: ...this is the location of the first definition
po/cs.po:3596: duplicate message definition...
po/cs.po:3094: ...this is the location of the first definition
msgfmt: found 4 fatal errors
gettext: po/de.po:3555: duplicate message definition...
po/de.po:900: ...this is the location of the first definition
po/de.po:3558: duplicate message definition...
po/de.po:905: ...this is the location of the first definition
po/de.po:3561: duplicate message definition...
po/de.po:2833: ...this is the location of the first definition
po/de.po:3564: duplicate message definition...
po/de.po:3062: ...this is the location of the first definition
msgfmt: found 4 fatal errors
gettext: po/es.po:3580: duplicate message definition...
po/es.po:914: ...this is the location of the first definition
po/es.po:3583: duplicate message definition...
po/es.po:919: ...this is the location of the first definition
po/es.po:3586: duplicate message definition...
po/es.po:2853: ...this is the location of the first definition
po/es.po:3589: duplicate message definition...
po/es.po:3085: ...this is the location of the first definition
msgfmt: found 4 fatal errors
gettext: po/fi.po:3473: duplicate message definition...
po/fi.po:893: ...this is the location of the first definition
po/fi.po:3476: duplicate message definition...
po/fi.po:897: ...this is the location of the first definition
po/fi.po:3479: duplicate message definition...
po/fi.po:2780: ...this is the location of the first definition
po/fi.po:3491: duplicate message definition...
po/fi.po:3000: ...this is the location of the first definition
msgfmt: found 4 fatal errors
gettext: po/fr.po:3484: duplicate message definition...
po/fr.po:889: ...this is the location of the first definition
po/fr.po:3487: duplicate message definition...
po/fr.po:893: ...this is the location of the first definition
po/fr.po:3490: duplicate message definition...
po/fr.po:2782: ...this is the location of the first definition
po/fr.po:3502: duplicate message definition...
po/fr.po:3010: ...this is the location of the first definition
msgfmt: found 4 fatal errors
gettext: po/gl.po:3564: duplicate message definition...
po/gl.po:936: ...this is the location of the first definition
po/gl.po:3567: duplicate message definition...
po/gl.po:941: ...this is the location of the first definition
po/gl.po:3570: duplicate message definition...
po/gl.po:2849: ...this is the location of the first definition
po/gl.po:3582: duplicate message definition...
po/gl.po:3072: ...this is the location of the first definition
msgfmt: found 4 fatal errors
gettext: po/hr.po:3456: duplicate message definition...
po/hr.po:893: ...this is the location of the first definition
po/hr.po:3459: duplicate message definition...
po/hr.po:897: ...this is the location of the first definition
po/hr.po:3462: duplicate message definition...
po/hr.po:2768: ...this is the location of the first definition
po/hr.po:3465: duplicate message definition...
po/hr.po:2989: ...this is the location of the first definition
msgfmt: found 4 fatal errors
gettext: po/hu.po:3499: duplicate message definition...
po/hu.po:892: ...this is the location of the first definition
po/hu.po:3502: duplicate message definition...
po/hu.po:896: ...this is the location of the first definition
po/hu.po:3505: duplicate message definition...
po/hu.po:2795: ...this is the location of the first definition
po/hu.po:3508: duplicate message definition...
po/hu.po:3023: ...this is the location of the first definition
msgfmt: found 4 fatal errors
gettext: po/it.po:3499: duplicate message definition...
po/it.po:892: ...this is the location of the first definition
po/it.po:3502: duplicate message definition...
po/it.po:896: ...this is the location of the first definition
po/it.po:3505: duplicate message definition...
po/it.po:2796: ...this is the location of the first definition
po/it.po:3517: duplicate message definition...
po/it.po:3019: ...this is the location of the first definition
msgfmt: found 4 fatal errors
gettext: po/ja.po:3540: duplicate message definition...
po/ja.po:938: ...this is the location of the first definition
po/ja.po:3543: duplicate message definition...
po/ja.po:943: ...this is the location of the first definition
po/ja.po:3546: duplicate message definition...
po/ja.po:2841: ...this is the location of the first definition
po/ja.po:3558: duplicate message definition...
po/ja.po:3061: ...this is the location of the first definition
msgfmt: found 4 fatal errors
gettext: po/ko.po:3578: duplicate message definition...
po/ko.po:950: ...this is the location of the first definition
po/ko.po:3581: duplicate message definition...
po/ko.po:955: ...this is the location of the first definition
po/ko.po:3584: duplicate message definition...
po/ko.po:2877: ...this is the location of the first definition
po/ko.po:3596: duplicate message definition...
po/ko.po:3098: ...this is the location of the first definition
msgfmt: found 4 fatal errors
gettext: po/pl.po:3533: duplicate message definition...
po/pl.po:893: ...this is the location of the first definition
po/pl.po:3536: duplicate message definition...
po/pl.po:897: ...this is the location of the first definition
po/pl.po:3539: duplicate message definition...
po/pl.po:2812: ...this is the location of the first definition
po/pl.po:3542: duplicate message definition...
po/pl.po:3039: ...this is the location of the first definition
msgfmt: found 4 fatal errors
gettext: po/pt_BR.po:3548: duplicate message definition...
po/pt_BR.po:904: ...this is the location of the first definition
po/pt_BR.po:3551: duplicate message definition...
po/pt_BR.po:909: ...this is the location of the first definition
po/pt_BR.po:3554: duplicate message definition...
po/pt_BR.po:2828: ...this is the location of the first definition
po/pt_BR.po:3566: duplicate message definition...
po/pt_BR.po:3054: ...this is the location of the first definition
msgfmt: found 4 fatal errors
gettext: po/ru.po:3480: duplicate message definition...
po/ru.po:889: ...this is the location of the first definition
po/ru.po:3483: duplicate message definition...
po/ru.po:893: ...this is the location of the first definition
po/ru.po:3486: duplicate message definition...
po/ru.po:2778: ...this is the location of the first definition
po/ru.po:3489: duplicate message definition...
po/ru.po:3000: ...this is the location of the first definition
msgfmt: found 4 fatal errors
gettext: po/sl.po:3419: duplicate message definition...
po/sl.po:922: ...this is the location of the first definition
po/sl.po:3422: duplicate message definition...
po/sl.po:926: ...this is the location of the first definition
po/sl.po:3425: duplicate message definition...
po/sl.po:2741: ...this is the location of the first definition
po/sl.po:3437: duplicate message definition...
po/sl.po:2950: ...this is the location of the first definition
msgfmt: found 4 fatal errors
gettext: po/sv.po:3492: duplicate message definition...
po/sv.po:932: ...this is the location of the first definition
po/sv.po:3495: duplicate message definition...
po/sv.po:937: ...this is the location of the first definition
po/sv.po:3498: duplicate message definition...
po/sv.po:2801: ...this is the location of the first definition
po/sv.po:3510: duplicate message definition...
po/sv.po:3013: ...this is the location of the first definition
msgfmt: found 4 fatal errors
gettext: po/ta.po:3510: duplicate message definition...
po/ta.po:892: ...this is the location of the first definition
po/ta.po:3513: duplicate message definition...
po/ta.po:896: ...this is the location of the first definition
po/ta.po:3516: duplicate message definition...
po/ta.po:2803: ...this is the location of the first definition
po/ta.po:3528: duplicate message definition...
po/ta.po:3028: ...this is the location of the first definition
msgfmt: found 4 fatal errors
gettext: po/tr.po:3553: duplicate message definition...
po/tr.po:918: ...this is the location of the first definition
po/tr.po:3556: duplicate message definition...
po/tr.po:923: ...this is the location of the first definition
po/tr.po:3559: duplicate message definition...
po/tr.po:2839: ...this is the location of the first definition
po/tr.po:3562: duplicate message definition...
po/tr.po:3063: ...this is the location of the first definition
msgfmt: found 4 fatal errors
gettext: po/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.