intercept(observable: Observable<Response>): Observable<Response> {
        return observable
        .map(response => {
            if (response.url.endsWith('/login')) {
                window.location.assign('/dsg/login?expired=true');
                return Observable.empty();
            }
            return response;
        })
        .catch(error => {
            if (error.status == 302 ||
                error.status == 401 && !error.url.endsWith('/login')) {
                window.location.assign('/dsg/login');
                return Observable.empty();
            } else if (error.status == 500 || error.status == 422) {
                this.exceptionObservable.notifyObservers(error);
            }
            return Observable.throw(error);
        });
    }