"The domain name you provided already exists" Continuous Deployment (CD) + Custom Domain Names

After following both the [Continuous Deployment (CD)](https://aws.github.io/chalice/topics/cd.html) and [Custom Domain Names](https://aws.github.io/chalice/topics/domainname.html) guides in the documentations. I'm not able to deploy by pushing to Github. The Beta stage is created but it fails with the message:

> "The domain name you provided already exists"

Long version:

```
Logical ID: ApiGatewayCustomDomain
Status: CREATE_FAILED
Status Reason: Resource handler returned message: "The domain name you provided already exists. (Service: ApiGateway, Status Code: 400, Request ID: a1f7ccd0-706f-4276-b5d2-a678276c793b, Extended Request ID: null)" (RequestToken: d5adf486-d4a1-721c-de04-c1bda238ee7d, HandlerErrorCode: AlreadyExists)
```

For clarification, I was able to properly deploy my app with the custom domain using `chalice deploy`, it's only when I push to Github and that triggers the cloud formation deploy that it fails, because the beta app is trying to use the same domain I'm already using. Is there a way to have this two "stages" use different domains?


Compare the Continuous Deployment and Custom Domain Names guides, then inspect the generated CloudFormation resource identified as ApiGatewayCustomDomain and the stage/domain configuration used by chalice deploy. Done means the GitHub-triggered deployment succeeds without the AlreadyExists error and the Beta and deployed stages can use distinct domains.

Written by the indexing model from the issue text.