add `Err` to `CopyResult`
diff --git a/openstack/objectstorage/v1/objects/requests.go b/openstack/objectstorage/v1/objects/requests.go
index 56004b2..9778de3 100644
--- a/openstack/objectstorage/v1/objects/requests.go
+++ b/openstack/objectstorage/v1/objects/requests.go
@@ -266,6 +266,7 @@
 		OkCodes:     []int{201},
 	})
 	res.Header = resp.HttpResponse.Header
+	res.Err = err
 	return res
 }