Error: You can have up to two API keys. Please delete older keys first.

## Problem
I've just encountered this problem when trying to add another API key after already using two.
```shell
$ croud api-keys create --output-fmt json
==> Error: You can have up to two API keys. Please delete older keys first.
```

## References
- https://github.com/crate/cratedb-toolkit/pull/81