type InvalidETag struct{}

func (e InvalidETag) Error() string {
	return "etag of the object has changed"
}

// BackendDown is returned for network errors
type BackendDown struct {
	Err string
}

func (e BackendDown) Error() string {
	return e.Err
}

// NotImplemented If a feature is not implemented
type NotImplemented struct {
	Message string
}