A newer version of the modfified WebConfiguration class fixed the problem. I found it at http://code.google.com/p/jsf-helloworld-2-appengine/source/browse/trunk/src/com/sun/faces/config/WebConfiguration.java?r=3 (for Mojarra 2.0.4)
see also: http://java.net/jira/browse/JAVASERVERFACES-1885 -- You received this message because you are subscribed to the Google Groups "Google App Engine for Java" group. To view this discussion on the web visit https://groups.google.com/d/msg/google-appengine-java/-/tdtFxFca8ZgJ. To post to this group, send email to google-appengine-java@googlegroups.com. To unsubscribe from this group, send email to google-appengine-java+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/google-appengine-java?hl=en.