问Google Calendar API创建事件返回403禁止，日历是公共的- PHP

EN

ini_set('display_errors', 1);
require 'Google/Client.php';
require 'Google/Service/Calendar.php';

session_start();

const CLIENT_ID = '**************.apps.googleusercontent.com';
const SERVICE_ACCOUNT_NAME = '**************@developer.gserviceaccount.com';
const KEY_FILE = '**************-privatekey.p12';

$client = new Google_Client();
$client->setApplicationName("Calendar App");
//$client->setUseObjects(true); //IF USING SERVICE ACCOUNT (YES)

if (isset($_SESSION['token'])) {
    $client->setAccessToken($_SESSION['token']);
}

$key = file_get_contents(KEY_FILE);
$client->setClientId(CLIENT_ID);
$client->setAssertionCredentials(new Google_Auth_AssertionCredentials(
SERVICE_ACCOUNT_NAME, 'https://www.google.com/calendar/feeds/**************@group.calendar.google.com/private/full/',
$key)
);

$client->setClientId(CLIENT_ID);

$cal = new Google_Service_Calendar($client);
$event = new Google_Service_Calendar_Event();
$event->setSummary('App Sum');
$event->setLocation('App Location');

$start = new Google_Service_Calendar_EventDateTime();
$start->setDateTime('2014-05-19T10:30:00.000-05:00');
$event->setStart($start);

$end = new Google_Service_Calendar_EventDateTime();
$end->setDateTime('2014-05-20T11:30:00.000-05:00');
$event->setEnd($end);

$attendeel = new Google_Service_Calendar_EventAttendee();
$attendeel->setEmail('**************@gmail.com');
$attendees = array($attendeel);
$event->attendees = $attendees;

$cal->events->insert('**************@group.calendar.google.com', $event);