Magento 2 The user specified as a definer does not exist

notification :

SQLSTATE[HY000]: General error: 1449 The user specified as a definer ('testuser'@'localhost') does not exist, query was: INSERT INTO `catalog_product_entity_media_gallery` (`attribute_id`, `value`, `media_type`) VALUES (?, ?, ?)

The steps below allow you to customize the definer:

Go to PHPMyAdmin
Select your Database
Select your table
Click on 'Triggers' in the top menu
Click 'Edit' to modify the trigger
Change definer from (e.g. [testuser@localhost] to your definer e.g. root@localhost

Good luck