code: func (d *Driver) checkLegacyDriver(short bool) error {
  	if d.ResourceGroup == "" {
  		if short {
  			return errors.New("new azure driver cannot manage old VMs, downgrade to v0.6.0")
  		}
  		return errors.New("new azure driver uses the new Azure Resource Manager APIs and therefore cannot manage this existing machine created with old azure driver. Please downgrade to docker-machine 0.6.0 to continue using these machines or to remove them")
  	}
  	return nil
  }
docs: // checkLegacyDriver errors out if it encounters an Azure VM created with the
  // legacy (<=0.6.0) docker-machine Azure driver.