drivers/azure/azure.go
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
}
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
}
// checkLegacyDriver errors out if it encounters an Azure VM created with the
// legacy (<=0.6.0) docker-machine Azure driver.