@Override
    protected void onError(final RequestContext context) {
        setResponseHeader(context);
    }
Behavior in case of SPNEGO authentication failure :
<ul><li>True : if SPNEGO is the last authentication method with no fallback.</li>
<li>False : if an interactive view (eg: login page) should be send to user as SPNEGO failure fallback</li>
</ul>
support/cas-server-support-spnego-webflow/src/main/java/org/apereo/cas/web/flow/SpnegoCredentialsAction.java