Django - automatically create User on Athlete create (tied together with a OneToOneField)

Question

I have a model called Athlete that has a OneToOne relation to the User model which is an AbstractUser, I'm trying to create a user whenever I create an Athlete and automatically tie them together but I'm getting an error:

Manager isn't available; 'auth.User' has been swapped for 'users.User'

Here's my User Model:

class User(AbstractUser):
    is_athlete = models.BooleanField(default=False)
    is_coach = models.BooleanField(default=False)
    is_owner = models.BooleanField(default=False)

    def save(self, *args, **kwargs):
        self.is_athlete = Athlete.objects.filter(user=self).exists()
        self.is_coach = Coach.objects.filter(user=self).exists()
        self.is_owner = Organization.objects.filter(owner=self).exists()
        super().save(*args, **kwargs)

and the Athlete Models (so far):

class Athlete(models.Model):
    user = models.OneToOneField(User, blank=True, null=True, on_delete=models.SET_NULL)
    coach = models.ForeignKey(Coach, blank=True, null=True, on_delete=models.SET_NULL, related_name='coach')

    def save(self, *args, **kwargs):
        try:
            User.objects.get(email=kwargs.get('email'))
            print('User with this mail already exists')
        except User.DoesNotExist:
            print('User with this mail does not exist')
            new_user = AuthUser.objects.create_user(email=email)
            self.user = new_user
            new_user.save()
        super().save(*args, **kwargs)

I'm calling AuthUser.objects.create_user because User is already the name of the User class, so I import the django auth user with:

from django.contrib.auth.models import User as AuthUser