RetryRequest get caught in MainServlet.java due to ICE-4261
The following causes the problem:
            //ICE-4261: We cannot wrap RuntimeExceptions as ServletExceptions because of support for Jetty
            //Continuations. However, if the message of a RuntimeException is null, Tomcat won't
            //properly redirect to the configured error-page. So we need a new RuntimeException
            //that actually includes a message.
            if( e.getMessage() != null ){
                throw e;
            }
            throw new RuntimeException("no message available",e);
I propose the following fix:
if (e.getMessage() != null || e.getClass().getCanonicalName().equals("org.mortbay.jetty.RetryRequest")) {
                throw e;
            }
            throw new RuntimeException("no message available",e);

Unfortunately I was writing a detailed review and I lost it. Damn firefox...