Q: Google Cloud Endpoint API returns 500 error I applied the answer found in 
HTTP code 302 encountered when deploying on Google App Engine Endpoints
The 302 problem is gone, the API has become visible in the deployed application, but now I'm getting this error:
{
 "error": {
  "errors": [
   {
    "domain": "global",
    "reason": "internalError",
    "message": "Internal Error"
   }
  ],
  "code": 500,
  "message": "Internal Error"
 }
}

The application log shows the 200 response for this request though:
2013-03-07 18:57:10.992 /_ah/spi/DeviceSyncEndPoint.listDevices 200 185ms 0kb Mozilla/5.0 (X11; Linux i686) AppleWebKit/537.11 (KHTML, like Gecko) Chrome/23.0.1271.95 Safari/537.11
216.31.219.19 - - [07/Mar/2013:18:57:10 -0800] "POST /_ah/spi/DeviceSyncEndPoint.listDevices HTTP/1.1" 200 86 - "Mozilla/5.0 (X11; Linux i686) AppleWebKit/537.11 (KHTML, like Gecko) Chrome/23.0.1271.95 Safari/537.11" "racermanager-hrd.appspot.com" ms=186 cpu_ms=47 cpm_usd=0.000010 instance=00c61b117ceb47410221ae438f2cbe7fc958

Where the 500 error is coming from and how do I  troubleshoot it?
