'Check that a submitted comment isn\'t a duplicate. This might be caused
by someone posting a comment twice. If it is a dup, silently return the *previous* comment.'

def check_for_duplicate_comment(self, new):

    possible_duplicates = self.get_comment_model()._default_manager.using(self.target_object._state.db).filter(content_type=new.content_type, object_pk=new.object_pk, user_name=new.user_name, user_email=new.user_email, user_url=new.user_url)
    for old in possible_duplicates:
        if ((old.submit_date.date() == new.submit_date.date()) and (old.comment == new.comment)):
            return old
    return new
