code: function passwd(oldPassword, newPassword, callback) {
      if (!deis._authenticated) {
        return callback(new Error('You need to login first'));
      }
  
      deis.client.post(format('/%s/auth/passwd', deis.version), {
        password: oldPassword,
        new_password: newPassword
      }, function(err, res, body) {
        if (err) {
          return callback(err);
        }
  
        if (res.statusCode === 200) {
          return callback(null);
        }
  
        return callback(new Error('Password change failed: ' + body.detail));
      });
    }
docs: change password
  @param  {String}   oldPassword current password
  @param  {String}   newPassword new password