In MySQL 8.0, the validate_password plugin was re-implemented as the validate_password component. The validate_password plugin is deprecated; expect it to be removed in a future version of MySQL.
(See https://dev.mysql.com/doc/mysql-security-excerpt/8.0/en/validate-password-transitioning.html
and
https://stackoverflow.com/questions/36301100/how-do-i-turn-off-the-mysql-password-validation)