Authentication issues should bubble up to the user

[Andrea Ieri]

I have recently tried deploying the ubuntu-advantage charm in an environment that did not have network access to the auth server. The charm went in an error state and carried a very generic error message:

  ubuntu-advantage/0* error idle 10.18.2.112 hook failed: "config-changed"

The charm debug logs were more helpful, showing that

subprocess.CalledProcessError: Command '['ubuntu-advantage', 'status', '--all', '--format', 'json']' returned non-zero exit status 1.

When trying the command manually on the unit, the client finally pointed me in the right direction

root@juju-f293f7-4-lxd-1:~# ubuntu-advantage status
Failed to connect to authentication server
Check your Internet connection and try again.

(although I needed strace to see which IP it was trying to reach)

I think it would be nice if the charm could display the actual CLI error in the juju status output.