Fatal error: Uncaught Error: Class "yii\validators\Validator" not found in /mnt/disk1/hosted/cuadro_mando/vendor/yiisoft/yii2/validators/RequiredValidator.php:18 Stack trace: #0 {main} thrown in /mnt/disk1/hosted/cuadro_mando/vendor/yiisoft/yii2/validators/RequiredValidator.php on line 18