Create new user

def _create_user(self, email, password, is_superuser, **extra_fields):
        """Create new user"""
        now = timezone.now()
        if not email:
            raise ValueError('The given email must be set')

        email = self.normalize_email(email)
        user = self.model(
            email=email,
            password=password,
            is_active=True,
            is_superuser=is_superuser, last_login=now,
            date_joined=now,
            **extra_fields)
        user.set_password(password)
        user.save(using=self._db)
        return user