code: public static void assertXMLValid(String xmlString, String systemId)
          throws SAXException, ConfigurationException {
          assertXMLValid(new Validator(xmlString, systemId));
      }
docs: Assert that a String containing XML contains valid XML: the String must
  contain a DOCTYPE to be validated, but the validation will use the
  systemId to obtain the DTD
  @param xmlString
  @param systemId
  @throws SAXException
  @throws ConfigurationException if validation could not be turned on
  @see Validator