Fatal error: Uncaught Error: Class 'yii\db\Migration' not found in /var/www/html/vendor/mdmsoft/yii2-admin/migrations/m160312_050000_create_user.php:6 Stack trace: #0 {main} thrown in /var/www/html/vendor/mdmsoft/yii2-admin/migrations/m160312_050000_create_user.php on line 6