def validate_uuid4(uuid_string):
    """
    Validate that a UUID string is in
    fact a valid uuid4.
    Happily, the uuid module does the actual
    checking for us.
    It is vital that the 'version' kwarg be passed
    to the UUID() call, otherwise any 32-character
    hex string is considered valid.
    """
    try:
        from uuid import UUID
        val = UUID(uuid_string, version=4)
    except ValueError:
        return False
    return val.hex == uuid_string.replace('-', '')
