def _prepare(self):
        self.message = force_text(self.message, strings_only=True)
        self.extra_tags = force_text(self.extra_tags, strings_only=True)
Prepares the message for serialization by forcing the ``message``
dataset/ETHPy150Open AppScale/appscale/AppServer/lib/django-1.5/django/contrib/messages/storage/base.py/Message._prepare