Meaningless error message

[dosas]

When sending an access_token request that returns an error, KeyError: 'access_token' is raised instead of a meaningful error message:

Wouldn't something like this be more meaningful?

#  token_data = {'error': 'invalid_grant', 'error_description': 'Invalid refresh token'}
if token_data.get("error") is None:
    raise RuntimeError(f'Obtaining access token failed: {token_data["error_description"]}')

self._access_token = token_data["access_token"]