Fatal error: Uncaught Error: Interface 'Magento\Framework\Event\ObserverInterface' not found in /home/esecureh/public_html/magdemo/vendor/magento/module-catalog-inventory/Observer/InvalidatePriceIndexUponConfigChangeObserver.php:18 Stack trace: #0 {main} thrown in /home/esecureh/public_html/magdemo/vendor/magento/module-catalog-inventory/Observer/InvalidatePriceIndexUponConfigChangeObserver.php on line 18