Comment 10 for bug 1447808

Upgrade from 14.10 to 15.04 broke programs' access to MariaDB because
they were all expecting to give a username of root and the appropriate
password. To repair, I set user.plugin back to empty for user='root'
and *also* had to set user.password as the upgrade had cleared it.

It's not nice to discover the problem after the reboot upgrade; I
didn't notice it in 15.04's release notes.

Suggesting a new user be created with the desired permissions and code
switch across to using that isn't practical when it's a legacy system
with much code in various languages and root/password scattered to the
winds by time. The client's system was being upgraded to get security
updates, not be pushed into changing their codebase for a security
improvement when no change wouldn't have worsened security.