Let TranslationDoesNotExist exception inherit from AttributeError
Let TranslationDoesNotExist exception inherit from AttributeError

This fixes error in templates, when accessing attributes which don't
have a translation. Instead, an empty value will be displayed instead.

zhangguiyu/django-parler,defivelo/django-parler,edoburu/django-parler,imposeren/django-parler,zhangguiyu/django-parler,ellmetha/django-parler,jrief/django-parler,imposeren/django-parler,defivelo/django-parler,django-parler/django-parler,ellmetha/django-parler,edoburu/django-parler,skirsdeda/django-parler,jrief/django-parler,django-parler/django-parler,HiddenData/django-parler,skirsdeda/django-parler,HiddenData/django-parler