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 bzflag 's PO files:

gettext: data/l10n/bzflag_en_US_l33t.po: can't guess language
gettext: data/l10n/bzflag_en_US_redneck.po: can't guess language
gettext: data/l10n/bzflag_ru.po:697: duplicate message definition...
data/l10n/bzflag_ru.po:22: ...this is the location of the first definition
data/l10n/bzflag_ru.po:795: duplicate message definition...
data/l10n/bzflag_ru.po:25: ...this is the location of the first definition
data/l10n/bzflag_ru.po:798: duplicate message definition...
data/l10n/bzflag_ru.po:28: ...this is the location of the first definition
data/l10n/bzflag_ru.po:801: duplicate message definition...
data/l10n/bzflag_ru.po:31: ...this is the location of the first definition
data/l10n/bzflag_ru.po:907: duplicate message definition...
data/l10n/bzflag_ru.po:34: ...this is the location of the first definition
data/l10n/bzflag_ru.po:1065: duplicate message definition...
data/l10n/bzflag_ru.po:40: ...this is the location of the first definition
data/l10n/bzflag_ru.po:1258: duplicate message definition...
data/l10n/bzflag_ru.po:43: ...this is the location of the first definition
data/l10n/bzflag_ru.po:1273: duplicate message definition...
data/l10n/bzflag_ru.po:46: ...this is the location of the first definition
data/l10n/bzflag_ru.po:1312: duplicate message definition...
data/l10n/bzflag_ru.po:49: ...this is the location of the first definition
data/l10n/bzflag_ru.po:1315: duplicate message definition...
data/l10n/bzflag_ru.po:67: ...this is the location of the first definition
data/l10n/bzflag_ru.po:2094: duplicate message definition...
data/l10n/bzflag_ru.po:61: ...this is the location of the first definition
data/l10n/bzflag_ru.po:2707: duplicate message definition...
data/l10n/bzflag_ru.po:64: ...this is the location of the first definition
msgfmt: found 12 fatal errors
gettext: data/l10n/bzflag_xx.po: xx 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.