[cas-dev] Assertion serialization in AbstractTicketValidationFilter with Tomcat 6.x

[Alar]

I get following error with Tomcat 6.0.14 and CAS Java Client 3.1:
---
java.lang.IllegalArgumentException: setAttribute: Non-serializable attribute
	org.apache.catalina.session.StandardSession.setAttribute(StandardSession.java:1293)
	org.apache.catalina.session.StandardSession.setAttribute(StandardSession.java:1254)
	org.apache.catalina.session.StandardSessionFacade.setAttribute(StandardSessionFacade.java:130)
	org.jasig.cas.client.validation.AbstractTicketValidationFilter.doFilter(AbstractTicketValidationFilter.java:112)
	org.springframework.web.filter.DelegatingFilterProxy.doFilter(DelegatingFilterProxy.java:138)
	org.jasig.cas.client.authentication.AuthenticationFilter.doFilter(AuthenticationFilter.java:103)

----

I belive that Assertion (AssertionImpl) should implement Serializable
in order to make tomcat happy. I think that Tomcat needs to have
everything serializable in session in order to support session
clustering.

Thanks,
Alar