Ability to force reuse of an existing build package?

Hey! I'd like to use Chalice for multi-environment deployments. I see that Chalice will automatically reuse a zip deployment package if it exists; for a deployment to prod, I would like the deployment to fail if the code was modified (i.e. fail if it doesn't find a ZIP file with the deployment that previously went to dev).

Is there an easy way to either:

1. Specify a deployment package to use
2. fail deployment if it doesn't find a cached zip package?

I can also take a look at adding support for this.

Start by tracing Chalice's existing automatic reuse of cached ZIP deployment packages and how deployments identify those packages. Done means deployments can either use a specified package or fail when the previously deployed package is not available or the code has changed.

Written by the indexing model from the issue text.