Comment 3 for bug 1755756

Thanks for including the traceback paste.

Looking at this, the error is being raised because the fmt.file_format of the parsed command output is None:

https://github.com/openstack/nova/blob/stable/queens/nova/virt/images.py#L162

and that attribute comes from the oslo_utils.imageutils parsing:

https://github.com/openstack/oslo.utils/blob/stable/queens/oslo_utils/imageutils.py#L65

So, this implies that the output of the 'qemu-img info' command doesn't have 'file format' in it. But we aren't logging the command output, so we don't know what it looks like ...