Comment 1 for bug 1726871

Yup the problem is right here, and it's been around since 2014:

https://github.com/openstack/nova/blob/16.0.0/nova/objects/block_device.py#L291

The regression that hits it is this:

https://review.openstack.org/#/c/429476/

Before that, that code didn't lazy-load bdm.instance and hit that code. And it would only fail if you're running nova-api with debug logging enabled (which isn't uncommon really).

Apparently we aren't hitting this in CI - probably because we don't gate on the NFS job.