"device_code" auth method returning as 400 "unknown grant type"

[dan phrawzty]

Hello,

I'm taking a go at hacking improved OAUTH2 support into the official (?) Python reference client. Said client uses the device_code auth method as described in the documentation.
Unfortunately I'm hitting what appears to be an API error. I can request and obtain the device code; however, when I attempt to begin polling the token endpoint, I immediately get a 400 and an error message.

Here's an HTTPie run (trimmed for brevity):

$ http -f POST https://services.rdio.com/oauth2/token Authorization:'Basic <trim>==' 'grant_type=device_code&device_code=ABCDEF'
HTTP/1.1 400 CODE = 400
Access-Control-Allow-Origin: *
Connection: keep-alive
Content-Language: en
Content-Length: 78
Content-Type: application/json
Date: Fri, 28 Aug 2015 13:39:48 GMT
P3P: CP="<trim>"
Server: nginx/1.2.4
Set-Cookie: <trim>; Domain=.rdio.com; Path=/
Vary: Accept-Language, Cookie
X-Version: 720
X-srv: srv-108-18

{
    "error": "unsupported_grant_type",
    "error_description": "unknown grant_type"
}

Has this auth method been disabled, deprecated, or otherwise rendered difficult to use? Is there a particular incantation necessary to make it go? Any insight would be appreciated.

Thanks!


--
dan.