Describe the bug
nixosTests.hocker-fetchdocker currently tries to download from the docker registry, which obviously doesn't work inside a VM test.

Still, it'd be nice to have a programmatic way to verify the tooling still works.

We should provide an alternative, maybe extend the test to also provide a registry, to which we push a minimal example, and then use the tooling to download it from there.

Notify maintainers
@ixmatus