Fix loading in Python 3.8 of code objects created under Python 3.7

[ManifoldFR]

I discovered that loading code objects created by higher order functions of the form

def make_fun(val):
    def func(_):
        return val
    return func

and pickled using cloudpickle in Python 3.7, can't be loaded back up again with load() in Python 3.8. I think this also affected dill (uqfoundation/dill#357).
A fix is suggested by one of the CPython devs here: python/cpython#12701 (comment)
This would mean making a fallback to pickle.load which is used.
I'm filing this issue so other people can see, this might be an example of why pickling for long term storage is not recommended.