code: public static XMLStreamException unsupportedElement(final XMLExtendedStreamReader reader, String supportedElement) {
          XMLStreamException ex = ControllerLogger.ROOT_LOGGER.unsupportedElement(
                  new QName(reader.getNamespaceURI(), reader.getLocalName(),reader.getPrefix()), reader.getLocation(), supportedElement);
  
          return new XMLStreamValidationException(ex.getMessage(),
                                                  ValidationError.from(ex, ErrorType.UNSUPPORTED_ELEMENT)
                                                          .element(reader.getName())
                                                          .alternatives(new HashSet<String>() {{add(supportedElement);}}),
                                                  ex);
      }
docs: Get an exception reporting a missing, required XML attribute.
  @param reader the stream reader
  @param supportedElement the element that is to be used in place of the unsupported one.
  @return the exception