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 git-cola 's PO files:

gettext: cola/i18n/cs.po:4061: duplicate message definition...
cola/i18n/cs.po:2413: ...this is the location of the first definition
msgfmt: found 1 fatal error
gettext: cola/i18n/de.po:937: duplicate message definition...
cola/i18n/de.po:934: ...this is the location of the first definition
cola/i18n/de.po:4098: duplicate message definition...
cola/i18n/de.po:2440: ...this is the location of the first definition
cola/i18n/de.po:4536: duplicate message definition...
cola/i18n/de.po:3219: ...this is the location of the first definition
msgfmt: found 3 fatal errors
gettext: cola/i18n/es.po:935: duplicate message definition...
cola/i18n/es.po:932: ...this is the location of the first definition
cola/i18n/es.po:4103: duplicate message definition...
cola/i18n/es.po:2437: ...this is the location of the first definition
msgfmt: found 2 fatal errors
gettext: cola/i18n/fr.po:934: duplicate message definition...
cola/i18n/fr.po:931: ...this is the location of the first definition
cola/i18n/fr.po:4100: duplicate message definition...
cola/i18n/fr.po:2436: ...this is the location of the first definition
msgfmt: found 2 fatal errors
gettext: cola/i18n/git-cola.pot:816: duplicate message definition...
cola/i18n/git-cola.pot:813: ...this is the location of the first definition
cola/i18n/git-cola.pot:3941: duplicate message definition...
cola/i18n/git-cola.pot:2311: ...this is the location of the first definition
msgfmt: found 2 fatal errors
gettext: cola/i18n/hu.po:931: duplicate message definition...
cola/i18n/hu.po:928: ...this is the location of the first definition
cola/i18n/hu.po:4099: duplicate message definition...
cola/i18n/hu.po:2433: ...this is the location of the first definition
msgfmt: found 2 fatal errors
gettext: cola/i18n/id_ID.po:871: duplicate message definition...
cola/i18n/id_ID.po:867: ...this is the location of the first definition
cola/i18n/id_ID.po:4111: duplicate message definition...
cola/i18n/id_ID.po:2409: ...this is the location of the first definition
msgfmt: found 2 fatal errors
gettext: cola/i18n/it.po:873: duplicate message definition...
cola/i18n/it.po:870: ...this is the location of the first definition
cola/i18n/it.po:3300: duplicate message definition...
cola/i18n/it.po:1034: ...this is the location of the first definition
cola/i18n/it.po:4213: duplicate message definition...
cola/i18n/it.po:2469: ...this is the location of the first definition
msgfmt: found 3 fatal errors
gettext: cola/i18n/ja.po:1003: duplicate message definition...
cola/i18n/ja.po:1000: ...this is the location of the first definition
cola/i18n/ja.po:4189: duplicate message definition...
cola/i18n/ja.po:2507: ...this is the location of the first definition
cola/i18n/ja.po:4605: duplicate message definition...
cola/i18n/ja.po:3289: ...this is the location of the first definition
msgfmt: found 3 fatal errors
gettext: cola/i18n/pl.po:981: duplicate message definition...
cola/i18n/pl.po:978: ...this is the location of the first definition
cola/i18n/pl.po:4162: duplicate message definition...
cola/i18n/pl.po:2486: ...this is the location of the first definition
msgfmt: found 2 fatal errors
gettext: cola/i18n/pt_BR.po:927: duplicate message definition...
cola/i18n/pt_BR.po:924: ...this is the location of the first definition
cola/i18n/pt_BR.po:4112: duplicate message definition...
cola/i18n/pt_BR.po:2435: ...this is the location of the first definition
msgfmt: found 2 fatal errors
gettext: cola/i18n/ru.po:891: duplicate message definition...
cola/i18n/ru.po:887: ...this is the location of the first definition
cola/i18n/ru.po:4116: duplicate message definition...
cola/i18n/ru.po:2422: ...this is the location of the first definition
cola/i18n/ru.po:4476: duplicate message definition...
cola/i18n/ru.po:3219: ...this is the location of the first definition
msgfmt: found 3 fatal errors
gettext: cola/i18n/sv.po:872: duplicate message definition...
cola/i18n/sv.po:869: ...this is the location of the first definition
cola/i18n/sv.po:4215: duplicate message definition...
cola/i18n/sv.po:2468: ...this is the location of the first definition
cola/i18n/sv.po:4568: duplicate message definition...
cola/i18n/sv.po:3300: ...this is the location of the first definition
msgfmt: found 3 fatal errors
gettext: cola/i18n/tr_TR.po:842: duplicate message definition...
cola/i18n/tr_TR.po:839: ...this is the location of the first definition
cola/i18n/tr_TR.po:3969: duplicate message definition...
cola/i18n/tr_TR.po:2337: ...this is the location of the first definition
msgfmt: found 2 fatal errors
gettext: cola/i18n/uk.po:923: duplicate message definition...
cola/i18n/uk.po:920: ...this is the location of the first definition
cola/i18n/uk.po:4119: duplicate message definition...
cola/i18n/uk.po:2441: ...this is the location of the first definition
msgfmt: found 2 fatal errors
gettext: cola/i18n/zh_CN.po:899: duplicate message definition...
cola/i18n/zh_CN.po:896: ...this is the location of the first definition
cola/i18n/zh_CN.po:4068: duplicate message definition...
cola/i18n/zh_CN.po:2403: ...this is the location of the first definition
cola/i18n/zh_CN.po:4421: duplicate message definition...
cola/i18n/zh_CN.po:3184: ...this is the location of the first definition
msgfmt: found 3 fatal errors
gettext: cola/i18n/zh_TW.po:977: duplicate message definition...
cola/i18n/zh_TW.po:974: ...this is the location of the first definition
cola/i18n/zh_TW.po:4152: duplicate message definition...
cola/i18n/zh_TW.po:2486: ...this is the location of the first definition
cola/i18n/zh_TW.po:4576: duplicate message definition...
cola/i18n/zh_TW.po:3268: ...this is the location of the first definition
msgfmt: found 3 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.