public String getDefaultFailureReason() {
    if(null == m_fails) {
      return null;
    }

    if(m_fails.size() == 1) {
      return m_fails.values().stream().findFirst().get();
    }

    return m_fails.get(DEFAULT);
  }
Gets the default failure reason associated with the {@link #DEFAULT} key.

@return the default failure reason.
ambari-server-spi/src/main/java/org/apache/ambari/spi/upgrade/UpgradeCheckDescription.java