Fatal error: Uncaught Error: Interface 'BraintreeHttp\Serializer' not found in /var/www/html/RIE/vendor/braintree/braintreehttp/lib/BraintreeHttp/Serializer/Multipart.php:17 Stack trace: #0 {main} thrown in /var/www/html/RIE/vendor/braintree/braintreehttp/lib/BraintreeHttp/Serializer/Multipart.php on line 17