docs: function createOauthClient(storagePath, clientSecrets) {
    var secrets = fs.readFileSync(path.join(storagePath,  clientSecrets + '.json'));
    if (secrets === undefined) { 
      throw new Error('failed to read secrets file');
    }
    secrets = JSON.parse(secrets);
  
    var gAuth = new googleAuth();
    var oauthClient = new gAuth.OAuth2(secrets.installed.client_id,
                                       secrets.installed.client_secret,
                                       secrets.installed.redirect_uris[0]);
    return oauthClient;
  }