code: public void error(XPathContext xctxt, String msg, Object[] args)
            throws javax.xml.transform.TransformerException
    {
  
      java.lang.String fmsg = XSLMessages.createXPATHMessage(msg, args);
  
      if (null != xctxt)
      {
        ErrorListener eh = xctxt.getErrorListener();
        TransformerException te = new TransformerException(fmsg, this);
  
        eh.fatalError(te);
      }
    }
docs: Tell the user of an error, and probably throw an
  exception.
  
  @param xctxt The XPath runtime context.
  @param msg An error msgkey that corresponds to one of the constants found
  in {@link org.apache.xpath.res.XPATHErrorResources}, which is
  a key for a format string.
  @param args An array of arguments represented in the format string, which
  may be null.
  
  @throws TransformerException if the current ErrorListoner determines to
  throw an exception.
  
  @throws javax.xml.transform.TransformerException