This is a custom user model that is known to work with Django 1.6 and django CMS 3.0.12 (probably all versions of CMS 3.0) and runs correctly on µWSGI.

admin.py

# -*- coding: utf-8 -*-

from __future__ import unicode_literals

from django.contrib import admin

from .models import Customer


class CustomerAdmin(admin.ModelAdmin):
    pass

admin.site.register(Customer, CustomerAdmin)

models.py

# -*- coding: utf-8 -*-
import re

from django.contrib.auth.models import AbstractBaseUser, PermissionsMixin, UserManager
from django.core import validators
from django.core.mail import send_mail
from django.db import models
from django.utils import timezone
from django.utils.http import urlquote
from django.utils.translation import ugettext_lazy as _


class CustomerManager(UserManager):

    def _create_user(self, email, password,
                     is_staff, is_superuser, **extra_fields):
        """
        Creates and saves a User with the given email and password.
        """
        now = timezone.now()
        if not email:
            raise ValueError('The given email must be set')
        email = self.normalize_email(email)
        user = self.model(email=email,
                          is_staff=is_staff, is_active=True,
                          is_superuser=is_superuser, last_login=now,
                          **extra_fields)
        user.set_password(password)
        user.save(using=self._db)
        return user

    def create_user(self, email, password=None, **extra_fields):
        return self._create_user(email, password, False, False,
                                 **extra_fields)

    def create_superuser(self, email, password, **extra_fields):
        return self._create_user(email, password, True, True,
                                 **extra_fields)


class Customer(AbstractBaseUser, PermissionsMixin):
    """
    An abstract base class implementing a fully featured User model with admin-
    compliant permissions. Primary difference is that this User Model doesn't
    use a discreet username. The primary identifier is the users' email address.
    Email and password are required. Other fields are optional.
    """
    email = models.CharField(_('email'), max_length=30, unique=True,
        help_text=_('Required. 30 characters or fewer. Letters, numbers and '
                    '@/./+/-/_ characters'),
        validators=[
            validators.RegexValidator(re.compile(
                '^[\w.@+-]+$'), _('Enter a valid email.'), 'invalid')])
    # email = models.EmailField(_('email address'), blank=True)
    is_staff = models.BooleanField(_('staff status'), default=False,
        help_text=_('Designates whether the user can log into this admin '
                    'site.'))
    is_active = models.BooleanField(_('active'), default=True,
        help_text=_('Designates whether this user should be treated as '
                    'active. Unselect this instead of deleting accounts.'))

    objects = CustomerManager()

    USERNAME_FIELD = 'email'
    REQUIRED_FIELDS = []

    class Meta:
        verbose_name = _('user')
        verbose_name_plural = _('users')

    def get_absolute_url(self):
        return "/users/%s/" % urlquote(self.email)

    def get_full_name(self):
        "Returns the short name for the user, which is the email address."
        return "A user called %s" % self.email

    def get_short_name(self):
        "Returns the short name for the user, which is the email address."
        return self.email

    def email_user(self, subject, message, from_email=None):
        """
        Sends an email to this User.
        """
        send_mail(subject, message, from_email, [self.email])

settings.py

...

INSTALLED_APPS = (
    ...
    'custom_user_model.apps.customers', # This is the app in my base project/apps containing the models.py and admin.py
    'cms',
    ....
    'custom_user_model',  # This is my base project
)

AUTH_USER_MODEL = 'customers.Customer'

...