/**
  * Instantiate quote and checkout
  *
  * @return EbayEnterprise_PayPal_CheckoutController
  * @throws Mage_Core_Exception
  */
 protected function _initCheckout()
 {
     $quote = $this->_getQuote();
     if (!$quote->hasItems() || $quote->getHasError()) {
         $this->getResponse()->setHeader('HTTP/1.1', '403 Forbidden');
         Mage::throwException($this->_helper->__('Unable to initialize Express Checkout.'));
     }
     $this->_checkout = Mage::getSingleton('ebayenterprise_paypal/express_checkout', array('helper' => $this->_helper, 'logger' => null, 'config' => $this->_config, 'quote' => $quote));
     $this->_checkout->setCustomerSession(Mage::getSingleton('customer/session'));
     return $this->_checkout;
 }