app/code/Magento/Authorizenet/Model/Directpost.php

...gento/Checkout/view/frontend/web/js/action/place-order.js

...agento/Checkout/view/frontend/web/js/model/place-order.js

app/code/Magento/Dhl/Model/Carrier.php

app/code/Magento/Fedex/Model/Carrier.php

.../Paypal/Controller/Express/AbstractExpress/PlaceOrder.php

...gento/Paypal/Controller/Express/AbstractExpress/Start.php

app/code/Magento/Paypal/Controller/Express/GetToken.php

app/code/Magento/Paypal/Model/Api/Nvp.php

app/code/Magento/Paypal/Model/Api/ProcessableException.php

app/code/Magento/Paypal/Model/Express.php

...o/Paypal/Test/Unit/Model/Api/ProcessableExceptionTest.php

app/code/Magento/Paypal/Test/Unit/Model/ExpressTest.php

...aypal/view/frontend/web/js/in-context/express-checkout.js

...end/web/js/view/payment/method-renderer/iframe-methods.js

...ew/payment/method-renderer/in-context/checkout-express.js