Dear Maintainer,

When there are multiple admininstrator users (set-up using Gnome
Settings -> Users) who are in the sudo group, the authentication dialog
that prompts for superuser access only displays the option to
authenticate as the first admin user.

Steps to reproduce:
1. On a clean sid install, create two aditional users in GNOME settings.
One user should be an Administrator, while the other should be a
Standard user. Set their passwords when creating the account.
2. Reboot and log on as the standard user
3. Try install software from GNOME Software. The authentication dialog
will only show the original user for authentication

I expected some clear way to change the user I wish to authenticate as
so that I could authenticate as any admin user.

I have not changed the default polkit config and so all users in the
sudo group are admin users in polkit's eyes. Verifying using groups
indicates that both admin users are in the sudo group.

https://gitlab.gnome.org/GNOME/gnome-shell/issues/352

This is still a problem.
And here's a scenario where it's worse! Which happened to me.

User "helena" is marked admin. But has never logged in, so as yet has
no password set.

User "barak" is logged in, and wants to run synaptic. That user is set
up to allow sudo with no password.

But oops, synaptic wants him to fill in helena's password. Which does not exist.

And the authentication dialog has grabbed everything: cannot exit or
abort, cannot switch virtual consoles. Completely unresponsive. Only
options are to hit the power button, or log in from another host via
ssh and figure out which is the bad process and kill it. Neither of
these are things we should require from a normal user.