newsupernova/vendor/magento/module-newsletter/Controller/Adminhtml/Problem.php

<?php
/**
 * Copyright © Magento, Inc. All rights reserved.
 * See COPYING.txt for license details.
 */
namespace Magento\Newsletter\Controller\Adminhtml;

/**
 * Newsletter subscribers controller
 */
abstract class Problem extends \Magento\Backend\App\Action
{
    /**
     * Authorization level of a basic admin session
     *
     * @see _isAllowed()
     */
    const ADMIN_RESOURCE = 'Magento_Newsletter::problem';
}