Hello.
Similarly to #243, some APIs may return detailed error message for 404 Not Found errors. For example:
{"itemNotFound": {"code": 404, "message": "Resource ... cannot be found."}}
It could be useful if ErrDefault404.Error() would show this detailed message instead of "Resource not found"
(https://github.com/gophercloud/gophercloud/blob/master/errors.go#L182)