The '{ d }' considered as an invalid key by the nova, but the HTTP status code is 200, in the response.
tempest.common.rest_client: INFO: Request: DELETE http://10.34.131.210:8774/v2/50b11029b6d44f41922610b3c7ed7379/servers/999/metadata/{ d }
tempest.common.rest_client: DEBUG: Request Headers: {'X-Auth-Token': '<Token omitted>'}
tempest.common.rest_client: INFO: Response Status: 200
tempest.common.rest_client: DEBUG: Response Body: <head>
<title>Error response</title>
</head>
<body>
<h1>Error response</h1>
<p>Error code 400.
<p>Message: Bad request syntax ('DELETE /v2/50b11029b6d44f41922610b3c7ed7379/servers/999/metadata/{ d } HTTP/1.1').
<p>Error code explanation: 400 = Bad request syntax or unsupported method.
</body>
You can modify tempest.tests.compute.servers.test_servers_metadata.test_delete_nonexistant_server_metadata_item in order to reproduce the issue.
I also wonder is HTML response format the default ?
so the issue is spaces in the request is rejected by our http server before it ever gets into our wsgi stack.