in src/main/java/com/cisco/gerrit/plugins/slack/client/WebhookClient.java [65:87]
  public boolean publish(String message, String webhookUrl) {
    if (message == null || message.equals("")) {
      throw new IllegalArgumentException("message cannot be null or empty");
    }
    if (webhookUrl == null || webhookUrl.equals("")) {
      throw new IllegalArgumentException("webhookUrl cannot be null or empty");
    }
    boolean result;
    result = false;
    String response;
    response = postRequest(message, webhookUrl);
    if ("ok".equals(response)) {
      result = true;
    } else {
      LOGGER.error("Unexpected response: [" + response + "].");
    }
    return result;
  }