I'm giving CF 225 and diego 0.1441.0 a run.
CF 225 is up and app deployed.
Stop app. cf enable-diego app. Start app:
FAILED
Server error, status code: 500, error code: 10001, message: An unknown error occurred.
FAILED
Server error, status code: 500, error code: 10001, message: An unknown error occurred.

CF_TRACE ends with:
REQUEST: [2015-12-09T17:17:37-05:00]
PUT /v2/apps/02c68ddd-0596-4aab-8c05-a8f538d06712?async=true&inline-relations-depth=1 HTTP/1.1
Host: api.dev.foo.com
Accept: application/json
Authorization: [PRIVATE DATA HIDDEN]
Content-Type: application/json
User-Agent: go-cli 6.14.0+2654a47 / darwin

{"state":"STARTED"}

RESPONSE: [2015-12-09T17:17:37-05:00]
HTTP/1.1 500 Internal Server Error
Content-Length: 99
Content-Type: application/json;charset=utf-8
Date: Wed, 09 Dec 2015 22:17:36 GMT
Server: nginx
X-Cf-Requestid: 6edf0ac8-384f-4db3-576a-6744b7eb4b8c
X-Content-Type-Options: nosniff
X-Vcap-Request-Id: 860d73f9-9415-478f-6c60-13e2e5ddde8c::80a4a687-7f2d-44c5-9b09-4e3c9fa07b68

{
"error_code": "UnknownError",
"description": "An unknown error occurred.",
"code": 10001
}


Where next to look for the broken piece?