Package update failures: Clearsigned file isn't valid, got 'NODATA'

I’ve been using GitLab-CE for a couple of years with great success (I’m on 12.x with latest Postgres), but it’s just started throwing these errors though I’ve not touched the config. I’m running it on Debian Jessie (8), which is supposedly still a supported platform, but the repo appears to be broken:

Ign https://packages.sury.org jessie/main Translation-en_US.UTF-8
100% [Sources 32.7 MB] [InRelease gpgv 0 B]Splitting up /var/lib/apt/lists/partial/packages.gitlab.com_gitlab_gitlab-ce_debian_dists_jessie_InReleErr https://packages.gitlab.com jessie InRelease

Get:19 https://download.docker.com jessie/stable Translation-en_US [587 B]
100% [Translation-en 0 B] [InRelease gpgv 0 B]Splitting up /var/lib/apt/lists/partial/packages.gitlab.com_runner_gitlab-runner_debian_dists_jessieErr https://packages.gitlab.com jessie InRelease

W: An error occurred during the signature verification. The repository is not updated and the previous index files will be used. GPG error: https://packages.gitlab.com jessie InRelease: Clearsigned file isn't valid, got 'NODATA' (does the network require authentication?)

W: An error occurred during the signature verification. The repository is not updated and the previous index files will be used. GPG error: https://packages.gitlab.com jessie InRelease: Clearsigned file isn't valid, got 'NODATA' (does the network require authentication?)

W: Failed to fetch https://packages.gitlab.com/gitlab/gitlab-ce/debian/dists/jessie/InRelease

W: Failed to fetch https://packages.gitlab.com/runner/gitlab-runner/debian/dists/jessie/InRelease

W: Some index files failed to download. They have been ignored, or old ones used instead.

I can’t find any mention of these errors in this forum. How can I fix this?

I found that running the repo installation script made the packages work again - I guess that gitlab changed repo keys.