If ''@'localhost' password is expired, then such user could not set a password

create user ''@localhost password expire;

connect(con1, localhost, u);

--error 1820

select user();

set password='';

MariaDB [(none)]> select user();

ERROR 1820 (HY000): You must SET PASSWORD before executing this statement

MariaDB [(none)]> set password='';

ERROR 1131 (42000): You are using MariaDB as an anonymous user and anonymous users are not allowed to modify user settings