swift3 - swift 3.0 中的 google plus 集成问题

Question

func finishedWithAuth(auth: GTMOAuth2Authentication!, error: NSError!) {
    let plusService :GTLServicePlus = GTLServicePlus.init()
    plusService.retryEnabled = true
    plusService.authorizer = GPPSignIn.sharedInstance().authentication
    plusService.apiVersion = "v1"

    let query : GTLQueryPlus = GTLQueryPlus.queryForPeopleGetWithUserId("me") as! GTLQueryPlus

    plusService.executeQuery(query) { (ticket,person, error) -> Void in
        if ((error) != nil) {
            //Handle Error
        } else {
           // NSLog("Email= %@", GPPSignIn.sharedInstance().authentication.userEmail)
           // NSLog("GoogleID=%@", person.identifier)
            print(person)
            print(person.aboutMe)
        }
    }

}

当我们在 GTMOAuth2Authentication 的 swift 3.0 中构建总是获得身份验证失败时，请您帮帮我