Fatal error: Uncaught Error: Class "PKP\migration\Migration" not found in /var/www/html/lib/pkp/classes/migration/upgrade/v3_5_0/I10962_UpdateEmailTemplateVariables.php:22 Stack trace: #0 {main} thrown in /var/www/html/lib/pkp/classes/migration/upgrade/v3_5_0/I10962_UpdateEmailTemplateVariables.php on line 22