Comment 1 for bug 1736101

In master and stable/pike, 409 error is returned in that case.

HTTP/1.1 409 Conflict
{"errors": [{"status": 409, "request_id": "req-f34c6774-0d39-4deb-8d51-cda4819387f6", "detail": "There was a conflict when trying to complete your request.\n\n Conflicting resource provider test already exists. ", "title": "Conflict"}]}

And a uncaught exception is not logged in the log file.

12月 06 15:26:19 devstack-master <email address hidden>[16874]: INFO nova.api.openstack.placement.requestlog [None req-f34c6774-0d39-4deb-8d51-cda4819387f6 admin admin] 10.0.2.15 "POST /placement/resource_providers" status: 409 len: 237 microversion: 1.10
12月 06 15:26:19 devstack-master <email address hidden>[16874]: [pid: 16876|app: 0|req: 2/4] 10.0.2.15 () {58 vars in 1006 bytes} [Wed Dec 6 15:26:19 2017] POST /placement/resource_providers => generated 237 bytes in 10 msecs (HTTP/1.1 409) 6 headers in 231 bytes (1 switches on core 0)

They are right behavior.

Environment
-----------
master: commit 9f46043f2f2463695385a6a14634664be4833e8e
stable/pike: commit 8f7f4b3ba6bb17e39fd3f2d22ed2457311988692