问如何在Angular 6中获取CatchError块中的API错误响应？

EN

POST /register 
{
    "success": false,
    "error": {
        "email": [
            "Enter a valid email address."
        ]
    }
}

register(username: string, email: string, password, first_name: string, last_name: string) {
        return this.http.post<any>(this.registerURL,
            {"username": username, "password": password, "email": email, "first_name": first_name,
                "last_name": last_name})
            .pipe(map(user => {
                    if (user && user.token) {
                        localStorage.setItem('token', user.token);
                    }
                    return user;
                }),
                catchError((error: any) => {
                    return throwError(error);
                })
            );
    }