juju charm resources cs:~jameinel/no-such-charm leaks whether the charm exists

[mhilton]

Migrated from: https://bugs.launchpad.net/juju/+bug/1710883

If I do:
$ juju-2.2.3p charm resources cs:~jameinel/ubuntu-litecl
No resources to display.

However, if I do:
$ juju-2.2.3p charm resources cs:~jameinel/ubuntu-lite

Then I'm prompted to do Ubuntu SSO.

However, as both are in a private namespace, I wouldn't expect the former to not ask for a password before finding out whether that object even exists or not.

I think the bug might be in the Charm store, I'm not sure.

@jameinel and @rogpeppe / @frankban pinged for this