# convert unicode strings in users_dict                                                                                                                                                                
            users = {}
            as_native_string = lambda s : s.encode('UTF-8') if isinstance(s, unicode) else s
            for i, v in self.users_dict.items():
                key = as_native_string(i)
                value = as_native_string(v)
                users[key] = value

            if not (allow_cookie_auth and self.is_valid(cookie)):
                digest_auth(self.realm, get_ha1_dict_plain(users),
                            self.secret)