Merge remote-tracking branch 'remotes/origin/MAGETWO-31559' into develop

Conflicts:
	app/code/Magento/Paypal/Helper/Shortcut/CheckoutValidator.php
	app/code/Magento/Paypal/Model/Express/Checkout.php
	app/code/Magento/Sales/Api/Data/OrderItemInterface.php
	dev/tests/integration/testsuite/Magento/Paypal/Model/Express/CheckoutTest.php
	dev/tests/static/testsuite/Magento/Test/Legacy/_files/obsolete_classes.php
	dev/tests/static/testsuite/Magento/Test/Legacy/_files/obsolete_methods.php
	dev/tests/unit/testsuite/Magento/Paypal/Helper/Shortcut/CheckoutValidatorTest.php

Author: Kostiantyn Poida

app/code/Magento/Sales/Api/Data/OrderItemInterface.php

@@ -264,7 +264,9 @@ interface OrderItemInterface extends \Magento\Framework\Api\ExtensibleDataInterf
      * Base hidden tax refunded.
      */
     const BASE_HIDDEN_TAX_REFUNDED = 'base_hidden_tax_refunded';
-    const IS_NOMINAL = 'is_nominal';
+    /*
+     * Tax canceled flag
+     */
     const TAX_CANCELED = 'tax_canceled';
     /*
      * Hidden-tax-canceled flag.