Handle error responses from API token endpoint

[mbthornton-lbl]

This PR seeks to address a failure where the Watcher gets a 401 unauthorized response from the jobs endpoint.

Underlying cause appears to be a non-200 return from the /token endpoint. This PR seeks to address this by:

• adding tenacity python lib to project
• decorating get_token with @retry with exponential backoff
• adding unit test for the above
• adding integration tests
• updating project.toml and .github action to not run @pytest.mark.integration tests

[shreddd]

Looks reasonable

[scanon]

This looks good.

You could add a few unit tests for this.

[aclum]

where is the 401 handling?