Problems to enable cors for Gateway Responses

Chalice only enable cors for success responses, but if the server responds bad requests, like unauthorized or forbidden, the browser receives cors errors. I'd like to apply the cors also to error responses managed by API gateway, in the same way panel does ([look at "Gateway Responses for"](https://i.stack.imgur.com/EejHv.png))

The issue names no file or test. Start by tracing Chalice's CORS handling and API Gateway gateway-response configuration, then verify that unauthorized and forbidden responses receive the same CORS headers as successful responses.

Written by the indexing model from the issue text.