Comment 9 for bug 1825239

We found a case there installing esm packages will fail with a 401.

ubuntu-advantage-tools needs apt (and libapt-pkg4.12) at version 1.0.1ubuntu2.22 or higher, otherwise it won't recognize the /etc/apt/auth.conf.d/90ubuntu-advantage file which is where the credentials are stored. apt older than 1.0.1ubuntu2.22 only knows about /etc/apt/auth.conf

Adding a depends on libapt-pkg4.12 (>= 1.0.1ubuntu2.22) to the ubuntu-advantage-tools package, perahps also on apt, should address this, but I worry about adding apt related dependencies to a package that will likely be upgraded in the same apt transaction. It's also something that other ua offerings doesn't need, like livepatch.

Another possibility is to add code to ubuntu-advantage-tools to install a newer apt if needed, when esm is enabled.