yii2/framework/yii/views/migration.php

<?php
/**
 * This view is used by console/controllers/MigrateController.php
 * The following variables are available in this view:
 *
 * @var string $className the new migration class name
 */
echo "<?php\n";
?>

use yii\db\Schema;

class <?= $className ?> extends \yii\db\Migration
{
	public function up()
	{

	}

	public function down()
	{
		echo "<?= $className ?> cannot be reverted.\n";
		return false;
	}
}