Failure if the default manager is not a CTEManager

[salomvary]

Given a model like this:

class Thing(models.Model):
    objects = models.Manager()
    cte_objects = CTEManager()

The following code:

cte = With(Thing.cte_objects.all())
cte.queryset().with_cte(cte)

fails with AttributeError: 'QuerySet' object has no attribute 'with_cte'

The documentation says:

Prerequisite: A Model with a “CTEManager”

Seems like the default manager is expected to be a CTEManager, not just "a" manager.

Not sure if this is a bug or a need for clarity on the default manager requirement in the documentation.