func IsFileNotFoundErr(err error) bool {
	if err == nil {
		return false
	}
	return fileNotFoundRe.MatchString(err.Error())
}
func IsFileNotFoundErr(err error) bool {
	if err == nil {
		return false
	}
	return fileNotFoundRe.MatchString(err.Error())
}
// IsFileNotFoundErr returns true if 'err' is an error message about a PFS
// file not being found