Comment 2 for bug 1830747

We can see here that the instance_group entry in the request spec is clearly missing the uuid even though there is a group scheduler hint:

    "instance_group": {
      "nova_object.name": "InstanceGroup",
      "nova_object.version": "1.11",
      "nova_object.data": {
        "members": null,
        "hosts": null,
        "policy": "anti-affinity"
      },
      "nova_object.namespace": "nova",
      "nova_object.changes": [
        "policy",
        "members",
        "hosts"
      ]
    },
    "scheduler_hints": {
      "group": [
        "295c99ea-2db6-469a-877f-454a3903a8d8"
      ]
    },

So I'm thinking we're somehow hitting this:

https://github.com/openstack/nova/blob/stable/rocky/nova/objects/request_spec.py#L228

saving that, and then hitting this which triggers the error:

https://github.com/openstack/nova/blob/stable/rocky/nova/objects/request_spec.py#L523