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