Port create_descriptors script to Python 3.

#!/usr/bin/env python2.7

#!/usr/bin/env python3

#

# This file is part of BridgeDB, a Tor bridge distribution system.

import random

import sys

import time

import ipaddr

import ipaddress

import math

import argparse

import hashlib

def get_random_ipv6_addr():

    valid_addr = None

    while not valid_addr:

        maybe = ipaddr.IPv6Address(random.getrandbits(128))

        maybe = ipaddress.IPv6Address(random.getrandbits(128))

        valid = check_ip_validity(maybe)

        if valid:

            valid_addr = maybe