Not related to the current pull request, but the two loops below are redundant and could be factored in a single dict-comprehension:

```python
    self._connections = {region: self._executor.submit(
        self._connect_module_to_regino,
        region,
        aws_access_key_id=aws_access_key_id,
        aws_secret_access_key=aws_secret_access_key
    ).result()}
```