hex encode a value.

def enhex_app(parser, cmd, args):  # pragma: no cover
    """
    hex encode a value.
    """

    parser.add_argument('value', help='the value to hex encode, read from stdin if omitted', nargs='?')
    parser.add_argument(
        '--separator', '-s',
        default='',
        help='the separator to place between hex tuples'
    )
    args = parser.parse_args(args)
    return enhex(pwnypack.main.binary_value_or_stdin(args.value), args.separator)