public static void renderHtmlErrorPage(FacesContext ctx, FacesException fe) {
ExternalContext extContext = ctx.getExternalContext();
if (!extContext.isResponseCommitted()) {
extContext.responseReset();
extContext.setResponseContentType("text/html; charset=UTF-8");
extContext.setResponseStatus(500);
try {
Writer w = extContext.getResponseOutputWriter();
DevTools.debugHtml(w, ctx, fe.getCause());