code: private void fail (final String logMessage) {
          LOGGER.error("negotiation error " + keySet + ": " + logMessage);
          negotiationStatus = NegotiationStatus.REJECTED;
      }
docs: Logs an error message containing all {@link #keySet} keys as well as the passed {@link String} parameter and
  indicates an unsuccessful negotiation by setting {@link #negotiationStatus} to {@link NegotiationStatus#REJECTED}
  .
  
  @param logMessage