discovery/openstack/openstack.go
func (c *SDConfig) UnmarshalYAML(unmarshal func(interface{}) error) error {
	*c = DefaultSDConfig
	type plain SDConfig
	err := unmarshal((*plain)(c))
	if err != nil {
		return err
	}
	if c.Role == "" {
		return errors.New("role missing (one of: instance, hypervisor)")
	}
	if c.Region == "" {
		return errors.New("openstack SD configuration requires a region")
	}
	return nil
}
func (c *SDConfig) UnmarshalYAML(unmarshal func(interface{}) error) error {
	*c = DefaultSDConfig
	type plain SDConfig
	err := unmarshal((*plain)(c))
	if err != nil {
		return err
	}
	if c.Role == "" {
		return errors.New("role missing (one of: instance, hypervisor)")
	}
	if c.Region == "" {
		return errors.New("openstack SD configuration requires a region")
	}
	return nil
}
// UnmarshalYAML implements the yaml.Unmarshaler interface.