Я пытаюсь вызвать Google People Api, но получаю ошибку 403

Question

Код:

$("#login-button").on('click', function() {
    $("#login-button").attr('disabled', 'disabled');

    // API call for Google login
    gapi.auth2.getAuthInstance().signIn().then(
        // On success
        function(success) { 
            // API call to get user information    

     gapi.client.request({ path: 'https://www.googleapis.com/plus/v1/people/me' }).then(   

                function(success) {            
                    console.log(success);
                    var user_info = JSON.parse(success.body);
                    console.log(user_info);  

                    $("#user-information div").eq(0).find("span").text(user_info.displayName);
                    $("#user-information div").eq(1).find("span").text(user_info.id);
                    $("#user-information div").eq(2).find("span").text(user_info.gender);
                    $("#user-information div").eq(3).find("span").html('<img src="' + user_info.image.url + '" />');
                    $("#user-information div").eq(4).find("span").text(user_info.emails[0].value);

                    $("#user-information").show();
                    $("#login-button").hide();
                },  

                function(error) {
                    $("#login-button").removeAttr('disabled');
                    alert('Error : Failed to get user user information');
                }
            ); 

        },

    );
});

Ошибка:

code :  403,
message : "The request is missing a valid API key.",
status : "PERMISSION_DENIED"