Wrapper of `django.contrib.messages.add_message`, that reads
        the message text from a template.

def add_message(self, request, level, message_template,
                    message_context=None, extra_tags=''):
        """
        Wrapper of `django.contrib.messages.add_message`, that reads
        the message text from a template.
        """
        if 'django.contrib.messages' in settings.INSTALLED_APPS:
            try:
                if message_context is None:
                    message_context = {}
                message = render_to_string(message_template,
                                           message_context).strip()
                if message:
                    messages.add_message(request, level, message,
                                         extra_tags=extra_tags)
            except TemplateDoesNotExist:
                pass