Executes the 'proposal create' subcommand.  Given a key file, and a
    series of key/value pairs, it generates batches of sawtooth_settings
    transactions in a BatchList instance.  The BatchList is either stored to a
    file or submitted to a validator, depending on the supplied CLI arguments.

def _do_config_proposal_create(args):
    """Executes the 'proposal create' subcommand.  Given a key file, and a
    series of key/value pairs, it generates batches of sawtooth_settings
    transactions in a BatchList instance.  The BatchList is either stored to a
    file or submitted to a validator, depending on the supplied CLI arguments.
    """
    settings = [s.split('=', 1) for s in args.setting]

    signer = _read_signer(args.key)

    txns = [_create_propose_txn(signer, setting)
            for setting in settings]

    batch = _create_batch(signer, txns)

    batch_list = BatchList(batches=[batch])

    if args.output is not None:
        try:
            with open(args.output, 'wb') as batch_file:
                batch_file.write(batch_list.SerializeToString())
        except IOError as e:
            raise CliException(
                'Unable to write to batch file: {}'.format(str(e)))
    elif args.sabre_output is not None:
        for i, txn in enumerate(txns):
            with open("{}-{}".format(args.sabre_output, i), 'wb') as outfile:
                outfile.write(txn.payload)
    elif args.url is not None:
        rest_client = RestClient(args.url)
        rest_client.send_batches(batch_list)
    else:
        raise AssertionError('No target for create set.')