[py3k] use the base64 module, instead of bytes.encode('base64')

from __future__ import unicode_literals

import base64

import hashlib

from django.dispatch import receiver

        if not iterations:

            iterations = self.iterations

        hash = pbkdf2(password, salt, iterations, digest=self.digest)

        hash = hash.encode('base64').strip()

        hash = base64.b64encode(hash).strip()

        return "%s$%d$%s$%s" % (self.algorithm, iterations, salt, hash)

    def verify(self, password, encoded):