When I try to update magento 2.1.9 to 2.2.0 I am getting this error
Fatal error: Uncaught Error: Cannot instantiate interface Magento\Framework\Serialize\SerializerInterface in vendor/magento/framework/ObjectManager/Factory/Dynamic/Developer.php
I try to edit app/etc/dl.xml
but I am not getting what to update in preference type
php bin/magento setup:upgrade
to fix that error. – Kingshuk Deb May 11 '18 at 9:49