Fatal error: Uncaught Error: Class "PKP\migration\Migration" not found in /var/www/html/lib/pkp/classes/migration/upgrade/v3_4_0/I9830_FixEmptyUserLocales.php:23 Stack trace: #0 {main} thrown in /var/www/html/lib/pkp/classes/migration/upgrade/v3_4_0/I9830_FixEmptyUserLocales.php on line 23