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 python-bottle 's PO files:

gettext: docs/_locale/zh_CN/async.po: can't guess language
gettext: docs/_locale/zh_CN/changelog.po: can't guess language
gettext: docs/_locale/zh_CN/configuration.po: can't guess language
gettext: docs/_locale/zh_CN/contact.po: can't guess language
gettext: docs/_locale/zh_CN/deployment.po: can't guess language
gettext: docs/_locale/zh_CN/development.po: can't guess language
gettext: docs/_locale/zh_CN/faq.po: faq not a language code
gettext: docs/_locale/zh_CN/index.po: can't guess language
gettext: docs/_locale/zh_CN/plugindev.po: can't guess language
gettext: docs/_locale/zh_CN/plugins.po: can't guess language
gettext: docs/_locale/zh_CN/recipes.po: can't guess language
gettext: docs/_locale/zh_CN/routing.po: can't guess language
gettext: docs/_locale/zh_CN/stpl.po: can't guess language
gettext: docs/_locale/zh_CN/tutorial.po: can't guess language
      

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.