Just display login with warning if Kerberos login failed

broker/kerberos/src/main/java/org/keycloak/broker/kerberos/KerberosIdentityProvider.java

@@ -107,9 +107,11 @@ public class KerberosIdentityProvider extends AbstractIdentityProvider<KerberosI
         Response response = request.getSession().getProvider(LoginFormsProvider.class)
                 .setRealm(request.getRealm())
                 .setUriInfo(request.getUriInfo())
-                .setError("errorKerberosLogin")
+                .setClient(request.getClientSession().getClient())
+                .setClientSessionCode(getRelayState(request))
+                .setWarning("errorKerberosLogin")
                 .setStatus(Response.Status.UNAUTHORIZED)
-                .createErrorPage();
+                .createLogin();
 
         response.getMetadata().putSingle(HttpHeaders.WWW_AUTHENTICATE, negotiateHeader);
         return AuthenticationResponse.fromResponse(response);

forms/common-themes/src/main/resources/theme/login/base/messages/messages.properties

@@ -98,7 +98,7 @@ actionPasswordWarning=You need to change your password to activate your account.
 actionEmailWarning=You need to verify your email address to activate your account.
 actionFollow=Please fill in the fields below.
 
-errorKerberosLogin=Unable to login with Kerberos
+errorKerberosLogin=Unable to login with Kerberos. Request Kerberos ticket or use different login mechanism
 
 successHeader=Success!
 errorHeader=Error!