Error in mintsources when clicking Add missing keys

[frostyturnip]

This happens on Mint 19.3 Cinnamon with a bare install and just fully updated. Open the Update Manager, navigate to Maintenance and click "Add missing keys". This generates the following in a box: "Error with your apt configuration, you may have to reload the cache first".

[xenopeek]

To reproduce:

• Fresh install without any added repositories;
• Click the "Add missing keys" in Maintenance section of Software Sources;
• Gives the message ""Error with your apt configuration, you may have to reload the cache first."

Clicking Refresh in Update Manager beforehand doesn't make a difference.

The cause looks to be the file /etc/apt/trusted.gpg doesn't exist until a repository is added to the system but the error handling code on "Add missing keys" checks for existence of the file /etc/apt/trusted.gpg, the directory /etc/apt/trusted.gpg.d/ and the directory /var/lib/apt/lists/ and if any of the three don't exist you get that message.

As that file /etc/apt/trusted.gpg doesn't exist by default, I think the error handling code should handle this differently and not have "Add missing keys" give an error.

[BLaDZer]

Bug still present in fresh installed Linux Mint 21.1 (XFCE) :-(