Hello. I'm getting the following error messages when executing sudo apt-get update:

W: GPG error: http://download.opensuse.org/repositories/home:/j_morgenroth/Debian_8.0 ./ Release: The following signatures were invalid: 144E39A7BA9845106A7FBFBA8984BBB839EBCBCA
W: The repository 'http://download.opensuse.org/repositories/home:/j_morgenroth/Debian_8.0 ./ Release' is not signed.
N: Data from such a repository can't be authenticated and is therefore potentially dangerous to use.
N: See apt-secure(8) manpage for repository creation and user configuration details.

I am using Raspberry Pi 3 with Raspbian Stretch (9.4) and I added the PGP key for Debian_8.0 distribution. 

I appreciate any assistance. Thank you.

Dominic B. Solpico
Research Engineer, Ateneo Innovation Center