How to use NavigationHandler during the Render Response phase - jsf

Question

I'm using JSF 2.2 (Mojarra) and Faclets in a web application. I use a custom ExceptionHandler to handle exceptions. I leverage the JSF implicit navigation system and cause the server to navigate to the 'error.xhtml' page.
public class FrontEndExceptionHandler extends ExceptionHandlerWrapper {
private ExceptionHandler wrapped;
FrontEndExceptionHandler(ExceptionHandler exception) {
this.wrapped = exception;
}
#Override
public ExceptionHandler getWrapped() {
return wrapped;
}
#Override
public void handle() throws FacesException {
final Iterator<ExceptionQueuedEvent> iter = getUnhandledExceptionQueuedEvents().iterator();
while (iter.hasNext()) {
ExceptionQueuedEvent event = iter.next();
ExceptionQueuedEventContext context = (ExceptionQueuedEventContext) event.getSource();
// get the exception from context
Throwable t = context.getException();
final FacesContext fc = FacesContext.getCurrentInstance();
final Flash flash = fc.getExternalContext().getFlash();
final NavigationHandler nav = fc.getApplication().getNavigationHandler();
try {
// redirect error page
flash.put("erorrDetails", t.getMessage());
nav.handleNavigation(fc, null, "/errors/error.xhtml");
fc.renderResponse();
} finally {
// remove it from queue
iter.remove();
}
}
// parent handle
getWrapped().handle();
}
}
This assumes that the exception to be handling is not happening during the Render Response phase. But the exception occurs within an Facelets page also during the Render Response phase.Therefore following code doesn't work correct:
nav.handleNavigation(fc, null, "/errors/error.xhtml");
Does anybody has a Idea how to convey the desired information? Is there a way to navigate to the error.xhtml without using NavigationHandler?