if i > 0 {
			msg += " or "
		}
		msg += "'" + examples[i] + "', "
	}
	msg += "regex used for validation is '" + fmt + "')"
	return msg
}

// EmptyError returns a string explanation of a "must not be empty" validation
// failure.
func EmptyError() string {
	return "must be non-empty"
}

func prefixEach(msgs []string, prefix string) []string {
	for i := range msgs {
		msgs[i] = prefix + msgs[i]
	}

	switch len(parts) {
	case 1:
		version = parts[0]
	case 2:
		var group string
		group, version = parts[0], parts[1]
		if len(group) == 0 {
			errs = append(errs, "group part: "+utilvalidation.EmptyError())
		} else if msgs := utilvalidation.IsDNS1123Subdomain(group); len(msgs) != 0 {
			errs = append(errs, prefixEach(msgs, "group part: ")...)
		}
	default: