NEWOBJ isn't a type object

[Simon King]

Hi!

Trying to make my group cohomology package work in both py2 and py3, I
already thought it was done, but I found that a pickle created with py3
cannot be read by py2. It would of course be possible to argue that people
are unlikely to unpickle a py3 pickle with py2, and since unpickling a
py2 pickle with py3 seems to work, we shouldn't care.

But just in case I wanted to ask if you know of an easy fix.

According to explain_pickle, the following happens:

sage: pg_RESL_sparse_unpickle_class =
unpickle_global('pGroupCohomology.resolution', 'RESL_sparse_unpickle_class')
sage: si1 = unpickle_newobj(pg_RESL_sparse_unpickle_class, ())
Traceback (most recent call last):
...
UnpicklingError: NEWOBJ class argument isn't a type object

What does that error mean? In fact, the class IS a type:

sage: from pGroupCohomology.resolution import RESL_sparse_unpickle_class
sage: isinstance(_, type)
True

Best regards,
Simon