Comment 4 for bug 1922251

The glance logs weren't very useful as the initial exception was being suppressed. Here are the key bits from Glance:

https://github.com/openstack/glance_store/blob/ae9022cd3639bf3d0f482921d03b2b751f757399/glance_store/location.py#L83-L113
https://github.com/openstack/glance/blob/b5437773b20db3d6ef20d449a8a43171c8fc7f69/glance/location.py#L122-L129

Basically Glance is throwing an UnknownScheme exception if the "store" metadata field is missing from the update request.