AUTH_USER_MODEL = "myapp.User"

from __future__ import unicode_literals
from django.db import models

from django.db import models
from django.utils import timezone
from django.contrib.auth.models import (
    AbstractBaseUser, PermissionsMixin
)

from django.contrib.auth.models import (
    AbstractBaseUser, PermissionsMixin, BaseUserManager
)


class UserManager(BaseUserManager):

    def _create_user(self, email, password, **extra_fields):
        """
        Creates and saves a User with the given email,and password.
        """
        if not email:
            raise ValueError('The given email must be set')
        try:
            with transaction.atomic():
                user = self.model(email=email, **extra_fields)
                user.set_password(password)
                user.save(using=self._db)
                return user
        except:
            raise

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

    def create_superuser(self, email, password, **extra_fields):
        extra_fields.setdefault('is_staff', True)
        extra_fields.setdefault('is_superuser', True)

        return self._create_user(email, password=password, **extra_fields)


class User(AbstractBaseUser, PermissionsMixin):
    """
    An abstract base class implementing a fully featured User model with
    admin-compliant permissions.

    """
    email = models.EmailField(max_length=40, unique=True)
    first_name = models.CharField(max_length=30, blank=True)
    last_name = models.CharField(max_length=30, blank=True)
    is_active = models.BooleanField(default=True)
    is_staff = models.BooleanField(default=False)
    date_joined = models.DateTimeField(default=timezone.now)

    objects = UserManager()

    USERNAME_FIELD = 'email'
    REQUIRED_FIELDS = ['first_name', 'last_name']

    def save(self, *args, **kwargs):
        super(User, self).save(*args, **kwargs)
        return self

AUTH_USER_MODEL = "myapp.User"

in resolve_related_fields
    raise ValueError('Related model %r cannot be resolved' % self.remote_field.model)
ValueError: Related model 'myapp.User' cannot be resolved