Error when adding a machine using root-disk-source volume in openstack

[Nicolas Vinuesa]

When trying to add a juju machine on an openstack cloud using the constraint `root-disk-source=volume`:
```
$ juju add-machine --constraints "root-disk-source=volume"
```

then we get the following error:

```
ubuntu@microstack2:~$ juju status
Model Controller Cloud/Region Version SLA Timestamp
m c openstack/microstack 3.1.6.1 unsupported 10:49:10+02:00

Machine State Address Inst id Base AZ Message
0 down pending ubuntu@22.04 cannot run instance: with fault "Build of instance 087c60f6-f8a1-48ce-899c-ffa73fbe8f0e aborted: Invalid input recei...
```

and from the debug logs:

```
controller-0: 10:48:47 ERROR juju.worker.provisioner cannot start instance for machine "0": cannot run instance: with fault "Build of instance 087c60f6-f8a1-48ce-899c-ffa73fbe8f0e aborted: Invalid input received: Invalid image identifier or unable to access requested image. (HTTP 400) (Request-ID: req-ffe40be6-bd91-4d23-8839-29a59c617129)"
```

Note: this was tested using microstack snap from channel latest/beta:
```
snap-id: qMvFl14Ge7zDRxjx4AGmBgsa4pNL9cYW
tracking: latest/beta
refresh-date: 8 days ago, at 23:12 CEST
channels:
  latest/stable: –
  latest/candidate: –
  latest/beta: ussuri 2023-04-18 (245) 438MB -
  latest/edge: ussuri 2022-01-21 (245) 438MB -
  sunbeam/stable: –
  sunbeam/candidate: –
  sunbeam/beta: yoga 2023-04-18 (388) 42MB -
  sunbeam/edge: yoga 2023-05-03 (389) 42MB -
  rocky/stable: –
  rocky/candidate: –
  rocky/beta: –
  rocky/edge: rocky 2019-12-06 (195) 398MB classic
installed: ussuri (245) 438MB -
```
and using juju 3.1.5

[Jack Shaw (jack-shaw)]

I have been unable to replicate this on canonistack (although I did use juju 3.2.1)

```
$ juju add-machine --constraints "root-disk-source=volume root-disk=7G"
created machine 3
(wait)
$ juju status
$ juju status
Model Controller Cloud/Region Version SLA Timestamp
m cstack canonistack/canonistack-bos01 3.2.1.1 unsupported 10:42:31+01:00

Machine State Address Inst id Base AZ Message
3 pending 10.48.129.204 5f9ec2d1-59e6-408b-8225-51bd6833b778 ubuntu@22.04 nova ACTIVE
```

Although it is weird that the vm is stuck in pending despite being ACTIVE

[Jack Shaw (jack-shaw)]

However, I get this exact error when trying to create a volume-backed instance in my Microstack manually

So this looks very much to be a specific Microstack thing, rather than Juju in my opinion