Session.get_credentials can return None

[aripollak]

Notes

This changes the type of Session.get_credentials() to allow returning None, which will happen here if no credentials are configured in the environment.

The aio* equivalents of this method might also be able to get similar changes, but I haven't tested those.

Type of change

• [x] Bug fix (non-breaking change which fixes an issue)
• [ ] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to not work as expected)

Checklist

All of these are optional:

• [x] I have performed a self-review of my own code
• [x] I have run ./scripts/before_commit.sh to follow the style guidelines of this project
• [ ] I have tested my code changes

Thank you!

[vemel]

Hello!

Thank you for your contribution. In order to keep compatibility with py37, please use Optional[Credentials] instead of Credentials | None.

[vemel]

LGTM! Thanks again!