code: public static XmlConfigurationSource create(Reader reader, int priority)
        throws ConfigurationException {
      return new XmlConfigurationSource(createConfiguration(reader), priority);
    }
docs: Creates an instance of {@link XmlConfigurationSource}.
  
  @throws ConfigurationException when fails to create the {@link XMLConfiguration}
  @throws NullPointerException if the path to the xml file is null
  @throws IllegalArgumentException if the path to the xml file is not valid or the
  priority is a  negative value