bad-exception-cause pylint error

[Yanks]

When catching `keystoneauth1.exceptions.http.Unauthorized` and re-raising from the caught exception, pylint complains about the caught exception not being an exception (which it does seem to be).

The error is: E0705: Exception cause set to something which is not an exception, nor None (bad-exception-cause)

when running pylint on the following code:

```
class CustomError(Exception):
    pass

except keystoneauth1.exceptions.http.Unauthorized as exc:
        raise CustomError( # pylint: disable=bad-exception-cause
            "Unauthorized to connect to OpenStack."
        ) from exc
```

[Pierre Sassoulas (pierre-sassoulas)]

Hello, pylint maintainer here, please report this in the pylint repo directly at https://github.com/pylint-dev/pylint/issues/new?assignees=&labels=Needs+triage+%3Ainbox_tray%3A&projects=&template=BUG-REPORT.yml