public static void handleWarning(final Node node, final String msg)
    {
        final ErrorHandler handler = (ErrorHandler)node.getOwnerDocument().getUserData(ERROR_HANDLER_KEY);
        if (null == handler)
        {
            throw new IllegalStateException("WARNING: " + formatLocationInfo(node) + msg);
        }
        else
        {
            handler.warning(formatLocationInfo(node) + msg);
        }
    }
Handle a warning condition as a consequence of parsing.

@param node as the context for the warning.
@param msg  associated with the warning.
sbe-tool/src/main/java/uk/co/real_logic/sbe/xml/XmlSchemaParser.java