anchor.diff:    String get algorithmName => "Null";
     void seed(CipherParameters params) {}
     int nextUint8() => Uint8.clip(_nextValue++);
  +}
  +
  +class AuthorizationError extends Error {
  +  String error;
  +  
  +  AuthorizationError(this.error);
  +  
  +  String toString() => "Authorisation error: $error";
   }
positive.code:       })
          .then((HttpClientResponse response) {
            return response.toList().then((list){
              auth = JSON.decode(new String.fromCharCodes(list.first));
              return auth;
            });
          });
  
negative.code:         })
            .then((HttpClientResponse response) {
              return response.toList().then((list){
                auth = JSON.decode(new String.fromCharCodes(list.expand((i) => i)));
                if (auth['error'] != null) {
                  throw new AuthorizationError(auth['error_description']);
                }
                return auth;
              });
            });
  