Catch CredentialChangeExhausted and show more information #107
Description
Amazonka throws CredentialChainExhausted when your AWS authorization is not configured.
We could catch this and explain the situation better to our users, for example:
No AWS credentials were found in your environment.
For details of where stackctl looks for credentials, see
<https://hackage.haskell.org/package/amazonka-2.0/docs/Amazonka-Auth.html#v:discover>