Ubuntu 18.04: Can't remove software key via software-properties package GUI

[SunBear]

I have these packages installed:

ii python3-software-properties 0.96.24.32.11 all manage the repositories that you install software from
ii software-properties-common 0.96.24.32.11 all manage the repositories that you install software from (common)
ii software-properties-gtk 0.96.24.32.11 all manage the repositories that you install software from (gtk)

However, after calling out `Software & Updates` GUI and clicking the `Authenication` tab, I found the `Remove` button there does not work. It does not delete any trusted software keys. I had to resort to using cli cmds as given in https://askubuntu.com/questions/107177/how-can-i-remove-gpg-key-that-i-added-using-apt-key-add/846877#846877 to remove any trusted software keys.

The 'Remove' button needs to work; it needs to be fixed.

**System information:**

$ lsb_release -rd
Description: Ubuntu 18.04.3 LTS
Release: 18.04

$ uname -a
Linux Machine 5.0.0-25-generic #26~18.04.1-Ubuntu SMP Thu Aug 1 13:51:02 UTC 2019 x86_64 x86_64 x86_64 GNU/Linux

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.