Hi pmong,
In OpenAPI 2.0, response examples can be specified using the examples.<media-type> keyword. Check out the Adding Examples guide for more information.
responses:
CONF001:
description: Configuration error
schema:
$ref: '#/definitions/ErrorModel'
examples:
application/json:
statusCode: CONF.001
statusMsg: Configuration error
Also, references to response definition (not schema definitions) should be like this:
400:
$ref: 'https://api.swaggerhub.com/domains/xxx/ErrorCodesDomain/1#/responses/DATA001'
After these changes your response example should work fine.