Handle CannotDeleteParentResourceProvider to 409 Conflict

Error handling to raise the exception 409 while deleting
the parent if it has children.

Closes-Bug: #1770636
Change-Id: I87df68992e4e635f009974f5205ca4919a4f2576

nova/api/openstack/placement/handlers/resource_provider.py

@@ -141,6 +141,10 @@ def delete_resource_provider(req):
     except exception.NotFound as exc:
         raise webob.exc.HTTPNotFound(
             _("No resource provider with uuid %s found for delete") % uuid)
+    except exception.CannotDeleteParentResourceProvider as exc:
+        raise webob.exc.HTTPConflict(
+            _("Unable to delete parent resource provider %(rp_uuid)s: "
+              "It has child resource providers.") % {'rp_uuid': uuid})
     req.response.status = 204
     req.response.content_type = None
     return req.response

nova/tests/functional/api/openstack/placement/gabbits/resource-provider.yaml

@@ -388,6 +388,13 @@ tests:
   response_strings:
       - 'un-parenting a provider is not currently allowed'
 
+- name: 409 conflict while trying to delete parent with existing child
+  DELETE: /resource_providers/$ENVIRON['PARENT_PROVIDER_UUID']
+  status: 409
+  response_strings:
+      - "Unable to delete parent resource provider
+       $ENVIRON['PARENT_PROVIDER_UUID']: It has child resource providers."
+
 - name: list all resource providers in a tree that does not exist
   GET: /resource_providers?in_tree=$ENVIRON['ALT_PARENT_PROVIDER_UUID']
   response_json_paths:

placement-api-ref/source/resource_provider.inc

@@ -106,6 +106,9 @@ A `409 Conflict` response code will be returned if there exist
 allocations records for any of the inventories that would be deleted
 as a result of removing the resource provider.
 
+This error code will be also returned if there are existing child resource
+providers under the parent resource provider being deleted.
+
 Request
 -------