When deleting an object via any relation (including when cascading

certain types of relations), we can end up in a situation where objects

can no longer be compared.
Model object comparisons check the primary key and model type. If one of

the primary keys is null, the model falls back to checking if the two

objects are the same exact instances.
What happens with deletion is that Django will perform a query

internally during delete object collection, delete them, and erase the

primary keys. This leads to several queries that are captured that

reference an object that no longer has a primary key and won't be the

same instances the unit test would have.
The solution to this is to listen in on object deletion and record any

primary keys being deleted. Then, during Q normalization, we can wrap

every model object referenced in a query to improve its equality checks,

factoring in instances that are deleted. This allows us to compare

instances.

All unit tests pass.
Tested this with unit tests in Review Board that were breaking due to

the deletion comparison behavior in Django.