Client error : Auth Error: net.sf.json.JSONException: JSONObject["return"] is not a JSONArray.

{"Error": "java.io.IOException: Server returned HTTP response code: 400 for URL: http://salt.example.com:8000/login

# tail -f /var/log/salt/master 
2015-09-28 11:28:45,306 [tornado.access   ][WARNING ][13082] 400 POST /login (192.168.10.50) 0.36ms

$ curl -sS http://salt.example.com:8000/login -H 'Accept: application/x-yaml' -d username='jenkins' -d password='jenkins' -d eauth='pam'                                  
*   Trying 192.168.10.50...
* Connected to salt.example.com (192.168.10.50) port 8000 (#0)
> POST /login HTTP/1.1
> Host: salt.example.com:8000
> User-Agent: Mozilla/5.0 (Windows NT 6.1; rv:31.0) Gecko/20100101 Firefox/31.0
> Referer: 
> Accept: application/x-yaml
> Content-Length: 54
> Content-Type: application/x-www-form-urlencoded
> 
* upload completely sent off: 54 out of 54 bytes
< HTTP/1.1 200 OK
< Date: Mon, 28 Sep 2015 10:52:46 GMT
< Content-Length: 186
< Content-Type: application/x-yaml
< Server: TornadoServer/4.2.1
< 
return:
- eauth: pam
  expire: 1443480766.019127
  perms: [test.*, pkg.*, cmd.*, state.*, '@runner']
  start: 1443437566.019126
  token: 8ad1cef834ee9df1a2eaff300c98a42c
  user: jenkins
* Connection #0 to host salt.example.com left intact

# salt-master --version
salt-master 2015.5.3 (Lithium)
# salt-api --version                                                                                                                                                                  
salt-api 2015.5.3