override couponpost.php
<preference for="Magento\Checkout\Controller\Cart\CouponPost" type="Vednor\Module\Controller\Rewrite\Cart\CouponPost" />
Crazy Cockroach
<preference for="Magento\Checkout\Controller\Cart\CouponPost" type="Vednor\Module\Controller\Rewrite\Cart\CouponPost" />