Django change translation fallback language

django_change_translation_fallback_language.py

# This is a hack so that French translation falls back to English translation,
# not German translation (which is the default locale and the original
# strings).
from django.utils.translation import trans_real


class MyDjangoTranslation(trans_real.DjangoTranslation):
    def _add_fallback(self, localedirs=None):
        if self._DjangoTranslation__language[:2] in {'de', 'en'}:
            return super()._add_fallback(localedirs)
        else:
            # Special case for French
            if self.domain == 'django':
                default_translation = trans_real.translation('en_GB')
            else:
                default_translation = self.__class__(
                    'en_GB', domain=self.domain, localedirs=localedirs)
            self.add_fallback(default_translation)


trans_real.DjangoTranslation = MyDjangoTranslation