Cannot prepare internal mirrorlist

We've an issue with the CentOS Docker image, as you can see in this pipeline:

Step 6/13 : RUN yum -y install openssh-server python3 &&     yum clean all &&     rm -rf /tmp/*
 ---> Running in e28bd7e5770b
CentOS Linux 8 - AppStream                      595  B/s |  38  B     00:00    
Error: Failed to download metadata for repo 'appstream': Cannot prepare internal mirrorlist: No URLs in mirrorlist
Service 'ssh' failed to build : The command '/bin/sh -c yum -y install openssh-server python3 &&     yum clean all &&     rm -rf /tmp/*' returned a non-zero code: 1

This is most likely related to this news post.

Let's investigate and see what we can do. Right now, we only need those images for HACTAR to run the patch tests against them / different OS'.