Add some error logging on saml-server

saml/saml.go

@@ -180,6 +180,7 @@ func (b *userFileBackend) GetSession(w http.ResponseWriter, r *http.Request, req
 	// configuration, is also verified at this stage.
 	username := httpsso.Username(r)
 	if username == "" {
+		log.Printf("error: could not retrieve user from SSO")
 		http.Error(w, "No user found", http.StatusInternalServerError)
 		return nil
 	}
@@ -191,6 +192,7 @@ func (b *userFileBackend) GetSession(w http.ResponseWriter, r *http.Request, req
 
 	user, ok := b.users[username]
 	if !ok {
+		log.Printf("error: user %s is authenticated but unknown", username)
 		http.Error(w, "User not found", http.StatusInternalServerError)
 		return nil
 	}