When executing:

client = Client.from_service_account_json('./key.json')

A TypeError is raised from oauth2client because the method create_scoped from oauth2client.service_account.ServiceAccountCredentials is called with scopes=None although this parameter expects an iterable.

Maybe the SCOPE variable in connection.py (line 69) should be an empty set instead of a None object ? I don't know what would be the side effects of such a change.