DateTime of version 3.0+ cannot be pickled without timezone

[georgpfolz]

• I am on the latest Pendulum version.

• [x ] I have searched the issues of this repo and believe that this is not a duplicate.

• OS version and name: MacOS Sonoma 14.6.1, FreeBSD 13.2

• Python: 3.11

• Pendulum version: 2.1.2, 3.0, 3.1.0

Issue

Pickling a pendulum DateTime does not work anymore.

import pickle, pendulum
dt = pendulum.now()
with open("datetime.pkl", "wb") as f:
    pickle.dump(dt, f)

This works fine with pendulum 2.1.2, but in 3.0 or 3.1.0 I get:

Traceback (most recent call last):
  File "<stdin>", line 2, in <module>
_pickle.PicklingError: Cannot pickle a ZoneInfo file from a file stream.

[georgpfolz]

After doing some more testing, I realized that the problem lies elsewhere: the pickling only fails if the tzinfo of the DateTime object is Timezone('None').

I wonder why in some cases the local timezone is not used, but the difference between the pendulum versions is that in pendulum 2.1.2 the non-existant tzinfo shows as Timezone('') (as opposed to Timezone('None') in 3.0+).

I ran into the problem because Zope's Ram Cache Manager (Products.StandardCacheManagers) threw exceptions after upgrading the pendulum version. The traceback showed the pickling error. But everything works fine with a valid timezone.