code: @Override
      public T call()
              throws Exception
      {
          T response = requestor.call();
  
          try {
              validateResponse( response );
              return response;
  
          } catch ( RuntimeException ex ) {
              if ( response instanceof Closeable ) {
                  PcsUtils.closeQuietly( ( Closeable ) response );
              }
              throw ex;
          }
      }
docs: Performs and validates http request.
  
  Two steps:<ol>
  <li>requests server with doRequest()</li>
  <li>validates response with validateResponse()</li>
  </ol>
  
  @return The request result
  @throws Exception Request invocation error