def validate_hostname(value, raise_exception=False):
    errors = []

    if not re.match(HOSTNAME_REGEX, value):
        errors.append('May only contain lowercase letters, numbers, and hyphens.')

    if value[0] == '-' or value[-1] == '-':
        errors.append('May not start or end with a hyphen.')

    if errors and raise_exception:
        raise ValidationError(errors)

    logger.debug(value)
    logger.debug(errors)

    return errors
dataset/ETHPy150Open stackdio/stackdio/stackdio/core/validators.py/validate_hostname/original