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 jwchat 's PO files:

gettext: po/._ru.po:1:1: syntax error
po/._ru.po:1: keyword "Mac" unknown
msgfmt: found 2 fatal errors
gettext: po/ca_ES.po:20: duplicate message definition...
po/ca_ES.po:6: ...this is the location of the first definition
msgfmt: found 1 fatal error
gettext: po/de.po:18: keyword "Really" unknown
po/de.po: warning: Charset missing in header.
                                                                 Message conversion to user's charset will not work.
po/de.po:17: duplicate message definition...
po/de.po:6: ...this is the location of the first definition
po/de.po:18:16: syntax error
po/de.po:18: keyword "destroy" unknown
po/de.po:19: end-of-line within string
po/de.po:22: end-of-line within string
msgfmt: found 6 fatal errors
gettext: po/en.po:20: duplicate message definition...
po/en.po:6: ...this is the location of the first definition
msgfmt: found 1 fatal error
gettext: po/es_ga.po: warning: Charset missing in header.
                                                                    Message conversion to user's charset will not work.
po/es_ga.po:17: duplicate message definition...
po/es_ga.po:6: ...this is the location of the first definition
msgfmt: found 1 fatal error
gettext: po/fr.po:1:2: syntax error
po/fr.po:18: keyword "pass" unknown
po/fr.po: warning: Charset missing in header.
                                                                 Message conversion to user's charset will not work.
po/fr.po:17: duplicate message definition...
po/fr.po:6: ...this is the location of the first definition
po/fr.po:18:14: syntax error
po/fr.po:18: keyword "is" unknown
po/fr.po:19: end-of-line within string
po/fr.po:21: end-of-line within string
po/fr.po:552: end-of-line within string
po/fr.po:1263:22: invalid control sequence
msgfmt: found 9 fatal errors
gettext: po/it.po:21: duplicate message definition...
po/it.po:6: ...this is the location of the first definition
msgfmt: found 1 fatal error
gettext: po/nl.po:27: duplicate message definition...
po/nl.po:7: ...this is the location of the first definition
msgfmt: found 1 fatal error
gettext: po/pt_br.po:21: duplicate message definition...
po/pt_br.po:6: ...this is the location of the first definition
msgfmt: found 1 fatal error
gettext: po/sk.po:16: duplicate message definition...
po/sk.po:2: ...this is the location of the first definition
po/sk.po:264: duplicate message definition...
po/sk.po:34: ...this is the location of the first definition
po/sk.po:328: duplicate message definition...
po/sk.po:42: ...this is the location of the first definition
po/sk.po:344: duplicate message definition...
po/sk.po:50: ...this is the location of the first definition
po/sk.po:348: duplicate message definition...
po/sk.po:59: ...this is the location of the first definition
po/sk.po:409: duplicate message definition...
po/sk.po:68: ...this is the location of the first definition
po/sk.po:491: duplicate message definition...
po/sk.po:76: ...this is the location of the first definition
po/sk.po:495: duplicate message definition...
po/sk.po:84: ...this is the location of the first definition
po/sk.po:539: duplicate message definition...
po/sk.po:93: ...this is the location of the first definition
po/sk.po:712: duplicate message definition...
po/sk.po:105: ...this is the location of the first definition
po/sk.po:721: duplicate message definition...
po/sk.po:117: ...this is the location of the first definition
po/sk.po:747: duplicate message definition...
po/sk.po:126: ...this is the location of the first definition
po/sk.po:1029: duplicate message definition...
po/sk.po:134: ...this is the location of the first definition
po/sk.po:1106: duplicate message definition...
po/sk.po:143: ...this is the location of the first definition
po/sk.po:1130: duplicate message definition...
po/sk.po:153: ...this is the location of the first definition
po/sk.po:1360: duplicate message definition...
po/sk.po:162: ...this is the location of the first definition
po/sk.po:1611: duplicate message definition...
po/sk.po:170: ...this is the location of the first definition
po/sk.po:1647: duplicate message definition...
po/sk.po:178: ...this is the location of the first definition
msgfmt: found 18 fatal errors
gettext: po/vi_VN.po: warning: Charset missing in header.
                                                                    Message conversion to user's charset will not work.
po/vi_VN.po: warning: Charset missing in header.
                                                                    Message conversion to user's charset will not work.
po/vi_VN.po:6: duplicate message definition...
po/vi_VN.po:3: ...this is the location of the first definition
po/vi_VN.po:201: duplicate message definition...
po/vi_VN.po:13: ...this is the location of the first definition
po/vi_VN.po:265: duplicate message definition...
po/vi_VN.po:19: ...this is the location of the first definition
po/vi_VN.po:281: duplicate message definition...
po/vi_VN.po:25: ...this is the location of the first definition
po/vi_VN.po:285: duplicate message definition...
po/vi_VN.po:32: ...this is the location of the first definition
po/vi_VN.po:346: duplicate message definition...
po/vi_VN.po:38: ...this is the location of the first definition
po/vi_VN.po:428: duplicate message definition...
po/vi_VN.po:44: ...this is the location of the first definition
po/vi_VN.po:432: duplicate message definition...
po/vi_VN.po:50: ...this is the location of the first definition
po/vi_VN.po:476: duplicate message definition...
po/vi_VN.po:57: ...this is the location of the first definition
po/vi_VN.po:649: duplicate message definition...
po/vi_VN.po:66: ...this is the location of the first definition
po/vi_VN.po:658: duplicate message definition...
po/vi_VN.po:73: ...this is the location of the first definition
po/vi_VN.po:684: duplicate message definition...
po/vi_VN.po:79: ...this is the location of the first definition
po/vi_VN.po:966: duplicate message definition...
po/vi_VN.po:85: ...this is the location of the first definition
po/vi_VN.po:1043: duplicate message definition...
po/vi_VN.po:92: ...this is the location of the first definition
po/vi_VN.po:1067: duplicate message definition...
po/vi_VN.po:99: ...this is the location of the first definition
po/vi_VN.po:1297: duplicate message definition...
po/vi_VN.po:105: ...this is the location of the first definition
po/vi_VN.po:1548: duplicate message definition...
po/vi_VN.po:111: ...this is the location of the first definition
po/vi_VN.po:1584: duplicate message definition...
po/vi_VN.po:117: ...this is the location of the first definition
msgfmt: found 18 fatal errors
gettext: po/zh_CN.po: warning: Charset missing in header.
                                                                    Message conversion to user's charset will not work.
po/zh_CN.po:17: duplicate message definition...
po/zh_CN.po:7: ...this is the location of the first definition
po/zh_CN.po:212: duplicate message definition...
po/zh_CN.po:24: ...this is the location of the first definition
po/zh_CN.po:276: duplicate message definition...
po/zh_CN.po:30: ...this is the location of the first definition
po/zh_CN.po:292: duplicate message definition...
po/zh_CN.po:36: ...this is the location of the first definition
po/zh_CN.po:296: duplicate message definition...
po/zh_CN.po:43: ...this is the location of the first definition
po/zh_CN.po:357: duplicate message definition...
po/zh_CN.po:49: ...this is the location of the first definition
po/zh_CN.po:439: duplicate message definition...
po/zh_CN.po:55: ...this is the location of the first definition
po/zh_CN.po:443: duplicate message definition...
po/zh_CN.po:61: ...this is the location of the first definition
po/zh_CN.po:487: duplicate message definition...
po/zh_CN.po:68: ...this is the location of the first definition
po/zh_CN.po:660: duplicate message definition...
po/zh_CN.po:77: ...this is the location of the first definition
po/zh_CN.po:669: duplicate message definition...
po/zh_CN.po:84: ...this is the location of the first definition
po/zh_CN.po:695: duplicate message definition...
po/zh_CN.po:90: ...this is the location of the first definition
po/zh_CN.po:977: duplicate message definition...
po/zh_CN.po:96: ...this is the location of the first definition
po/zh_CN.po:1054: duplicate message definition...
po/zh_CN.po:103: ...this is the location of the first definition
po/zh_CN.po:1078: duplicate message definition...
po/zh_CN.po:110: ...this is the location of the first definition
po/zh_CN.po:1308: duplicate message definition...
po/zh_CN.po:116: ...this is the location of the first definition
po/zh_CN.po:1559: duplicate message definition...
po/zh_CN.po:122: ...this is the location of the first definition
po/zh_CN.po:1595: duplicate message definition...
po/zh_CN.po:128: ...this is the location of the first definition
msgfmt: found 18 fatal errors
      

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.