Validates a timeout specified in milliseconds returning
    a value in floating point seconds for the case where None is an error
    and 0 is valid. Setting the timeout to nothing in the URI string is a
    config error.

def validate_timeout_or_zero(option, value):
    """Validates a timeout specified in milliseconds returning
    a value in floating point seconds for the case where None is an error
    and 0 is valid. Setting the timeout to nothing in the URI string is a
    config error.
    """
    if value is None:
        raise ConfigurationError("%s cannot be None" % (option, ))
    if value == 0 or value == "0":
        return 0
    return validate_positive_float(option, value) / 1000.0