// challenges, and that each challenges is also a comma separated list,
// but of parameters.
skipSpaces();
if (peek() != -1) {
String scheme = readToken();
result = new ChallengeRequest(new ChallengeScheme("HTTP_" + scheme,
scheme));
skipSpaces();
// Header writer that will reconstruct the raw value of a challenge.
HeaderWriter<Parameter> w = new HeaderWriter<Parameter>() {