code: protected final String exceptionMessage(String msg) {
          if (msg == null) {
              msg = "";
          }
  
          StringBuilder buf = new StringBuilder(128 + msg.length())
              .append(protocol())
              .append(", ")
              .append(authScheme())
              .append(", ")
              .append(proxyAddress)
              .append(" => ")
              .append(destinationAddress);
          if (!msg.isEmpty()) {
              buf.append(", ").append(msg);
          }
  
          return buf.toString();
      }
docs: Decorates the specified exception message with the common information such as the current protocol,
  authentication scheme, proxy address, and destination address.