Authentication prompt when changing brightness

[David Wilson]

Hi all,

This is my first attempt at setting up Guix on my machine, so please forgive me 
if I've missed anything obvious here. I've noticed that any time a process 
tries to set the backlight brightness of my laptop, a root authentication 
prompt appears:

https://imgur.com/a/vlB7UtN

I've seen this both when using xfce4-power-manager and inexplicably on the GDM 
login screen when I didn't even press a brightness key. It definitely seems 
like some policy configuration isn't set up correctly but I'm not exactly sure 
how to correct it.

I've configured my machine to use only the XFCE desktop environment but in 
practice I'm actually using a custom .xsession to launch Emacs with EXWM as my 
window manager. I believe I also saw it when running in XFCE but I can't repro 
it now due to a separate issue with xfwm crashing when XFCE starts up.

Here's my current system configuration if it helps:

https://github.com/daviwil/dotfiles/blob/23743190b8f744f89a8a43da6180576638246f72/guix/systems/zerocool.scm

I'm sure this must be a simple configuration issue so any help would be very 
much appreciated!

Thanks!

David