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 kcachegrind 's PO files:

gettext: poqm/ast/kcachegrind_qt.po: qt not a language code
gettext: poqm/bg/kcachegrind_qt.po: qt not a language code
gettext: poqm/bs/kcachegrind_qt.po: qt not a language code
gettext: poqm/ca/kcachegrind_qt.po: qt not a language code
gettext: poqm/ca@valencia/kcachegrind_qt.po: qt not a language code
gettext: poqm/cs/kcachegrind_qt.po: qt not a language code
gettext: poqm/da/kcachegrind_qt.po: qt not a language code
gettext: poqm/de/kcachegrind_qt.po: qt not a language code
gettext: poqm/el/kcachegrind_qt.po: qt not a language code
gettext: poqm/en/kcachegrind_qt.po: qt not a language code
gettext: poqm/en_GB/kcachegrind_qt.po: qt not a language code
gettext: poqm/eo/kcachegrind_qt.po: qt not a language code
gettext: poqm/es/kcachegrind_qt.po: qt not a language code
gettext: poqm/et/kcachegrind_qt.po: qt not a language code
gettext: poqm/eu/kcachegrind_qt.po: qt not a language code
gettext: poqm/fi/kcachegrind_qt.po: qt not a language code
gettext: poqm/fr/kcachegrind_qt.po: qt not a language code
gettext: poqm/ga/kcachegrind_qt.po: qt not a language code
gettext: poqm/gl/kcachegrind_qt.po: qt not a language code
gettext: poqm/hr/kcachegrind_qt.po: qt not a language code
gettext: poqm/hu/kcachegrind_qt.po: qt not a language code
gettext: poqm/ia/kcachegrind_qt.po: qt not a language code
gettext: poqm/it/kcachegrind_qt.po: qt not a language code
gettext: poqm/ja/kcachegrind_qt.po: qt not a language code
gettext: poqm/ka/kcachegrind_qt.po: qt not a language code
gettext: poqm/kk/kcachegrind_qt.po: qt not a language code
gettext: poqm/ko/kcachegrind_qt.po: qt not a language code
gettext: poqm/lt/kcachegrind_qt.po: qt not a language code
gettext: poqm/mai/kcachegrind_qt.po: qt not a language code
gettext: poqm/mr/kcachegrind_qt.po: qt not a language code
gettext: poqm/nb/kcachegrind_qt.po: qt not a language code
gettext: poqm/nds/kcachegrind_qt.po: qt not a language code
gettext: poqm/nl/kcachegrind_qt.po: qt not a language code
gettext: poqm/nn/kcachegrind_qt.po: qt not a language code
gettext: poqm/pl/kcachegrind_qt.po: qt not a language code
gettext: poqm/pt/kcachegrind_qt.po: qt not a language code
gettext: poqm/pt_BR/kcachegrind_qt.po: qt not a language code
gettext: poqm/ru/kcachegrind_qt.po: qt not a language code
gettext: poqm/se/kcachegrind_qt.po: qt not a language code
gettext: poqm/sk/kcachegrind_qt.po: qt not a language code
gettext: poqm/sl/kcachegrind_qt.po: qt not a language code
gettext: poqm/sv/kcachegrind_qt.po: qt not a language code
gettext: poqm/tr/kcachegrind_qt.po: qt not a language code
gettext: poqm/ug/kcachegrind_qt.po: qt not a language code
gettext: poqm/uk/kcachegrind_qt.po: qt not a language code
gettext: poqm/zh_CN/kcachegrind_qt.po: qt not a language code
gettext: poqm/zh_TW/kcachegrind_qt.po: qt 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.