Migration rollback not performed on index

Migration rollback not performed ?

When I create a table with an index and when the index fails due to a contraint

then the table is not removed (rolled back)

Any idea what is going on?

function safeUp()

{

$this->createTable(’{{%system_log}}’,

    [


            'id' => $this->bigPrimaryKey(),


            'level' => $this->integer(),                


        ], $tableOptions);





        $this->createIndex('idx_log_level', '{{%system_log}}', 'level');