API key should default to None and be an optional argument
API key should default to None and be an optional argument

jonparrott/oauth2client,googleapis/oauth2client,google/oauth2client,googleapis/google-api-python-client,googleapis/oauth2client,clancychilds/oauth2client,clancychilds/oauth2client,googleapis/google-api-python-client,jonparrott/oauth2client,google/oauth2client