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 stellarium 's PO files:

source does not specify a priority
gettext: po/stellarium-planetary-features/es_419.po: can't guess language
gettext: po/stellarium-remotecontrol/es_419.po: can't guess language
gettext: po/stellarium-scripts/es_419.po: can't guess language
gettext: po/stellarium-sky/es_419.po: can't guess language
gettext: po/stellarium-skycultures-descriptions/es_419.po: can't guess language
gettext: po/stellarium-skycultures-descriptions/stellarium-skycultures-descriptions.pot:2100: duplicate message definition...
po/stellarium-skycultures-descriptions/stellarium-skycultures-descriptions.pot:3: ...this is the location of the first definition
msgfmt: found 1 fatal error
gettext: po/stellarium-skycultures/es_419.po: can't guess language
gettext: po/stellarium/es_419.po: can't guess language
gettext: po/stellarium/te.po:7079: 'msgid' and 'msgstr' entries do not both end with '\n'
msgfmt: found 1 fatal error
      

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.