In my case, I was getting this error because I didn't have a PolicyKit authentication agent running. Launching `/usr/lib/policykit-1-gnome/polkit-gnome-authentication-agent-1` before running usb-creator-gtk fixed this issue for me.
In my case, I was getting this error because I didn't have a PolicyKit authentication agent running. Launching `/usr/lib/ policykit- 1-gnome/ polkit- gnome-authentic ation-agent- 1` before running usb-creator-gtk fixed this issue for me.