code: public void sendChallenge(UserRealm realm, HttpResponse response) throws IOException
      {
          response.setField(HttpFields.__WwwAuthenticate,"basic realm=\""+realm.getName()+'"');
  
          ServletHttpResponse sresponse = (ServletHttpResponse) response.getWrapper();
          if (sresponse!=null)
              sresponse.sendError(HttpResponse.__401_Unauthorized);
          else
              response.sendError(HttpResponse.__401_Unauthorized);
      }
docs: /*
  @see org.browsermob.proxy.jetty.http.BasicAuthenticator#sendChallenge(org.browsermob.proxy.jetty.http.UserRealm, org.browsermob.proxy.jetty.http.HttpResponse)