Comment 0 for bug 1903776

Since bionic, ubuntu-keyring removed `/etc/apt/trusted.gpg` in favor of `/etc/apt/trusted.gpg.d/`

This breaks signature verification for the upgrade-tool.
Trying to release-upgrade through landscape yields a failure on signature check:

2020-11-10 15:47:51,019 WARNING [MainThread] Invalid signature for upgrade-tool tarball: /usr/bin/gpg failed (out='', err='gpg: keybox '/etc/apt/trusted.gpg' created
gpg: Signature made Fri Oct 16 03:28:09 2020 UTC
gpg: using RSA key 3B4FE6ACC0B21F32
gpg: Can't check signature: No public key