def make_insecure_stub(stub_class, host, port=None):
    """Makes an insecure stub for an RPC service.

    Uses / depends on gRPC.

    :type stub_class: type
    :param stub_class: A gRPC stub type for a given service.

    :type host: str
    :param host: The host for the service. May also include the port
                 if ``port`` is unspecified.

    :type port: int
    :param port: (Optional) The port for the service.

    :rtype: object, instance of ``stub_class``
    :returns: The stub object used to make gRPC requests to a given API.
    """
    if port is None:
        target = host
    else:
        # NOTE: This assumes port != http_client.HTTPS_PORT:
        target = "%s:%d" % (host, port)
    channel = grpc.insecure_channel(target)
    return stub_class(channel)