Test failures with Python 3.11

Description

I’m building astropy 5.1 with a prerelease of python 3.11 for the next Fedora release. I’m getting this error in the tests:

=================================== FAILURES ===================================
_______ test_simple_object[0-StaticMatrixTransform-args6-kwargs6-False] ________
pickle_protocol = 0
name = <class 'astropy.coordinates.transformations.StaticMatrixTransform'>
args = [array([[1., 0., 0.],
       [0., 1., 0.],
       [0., 0., 1.]]), <class 'astropy.coordinates.builtin_frames.icrs.ICRS'>, <class 'astropy.coordinates.builtin_frames.icrs.ICRS'>]
kwargs = {}, xfail = False
    @pytest.mark.parametrize(("name", "args", "kwargs", "xfail"),
                             zip(_names, _args, _kwargs, _xfail))
    def test_simple_object(pickle_protocol, name, args, kwargs, xfail):
        # Tests easily instantiated objects
        if xfail:
            pytest.xfail()
        original = name(*args, **kwargs)
>       check_pickling_recovery(original, pickle_protocol)
astropy/coordinates/tests/test_pickle.py:71: 
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 
astropy/tests/helper.py:446: in check_pickling_recovery
    generic_recursive_equality_test(original, unpickled,
astropy/tests/helper.py:433: in generic_recursive_equality_test
    generic_recursive_equality_test(dict_a[key],
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 
a = <class 'astropy.coordinates.builtin_frames.icrs.ICRS'>
b = <class 'astropy.coordinates.builtin_frames.icrs.ICRS'>
class_history = [<class 'abc.ABCMeta'>, <class 'astropy.coordinates.transformations.StaticMatrixTransform'>]
    def generic_recursive_equality_test(a, b, class_history):
        """
        Check if the attributes of a and b are equal. Then,
        check if the attributes of the attributes are equal.
        """
>       dict_a = a.__getstate__() if hasattr(a, '__getstate__') else a.__dict__
E       TypeError: unbound method object.__getstate__() needs an argument
astropy/tests/helper.py:415: TypeError

This is probably related with a change in how objects are pickled. Now object has a default implementation of `getstate

https://docs.python.org/3.11/library/pickle.html#object.__getstate__

Full details in the Fedora bug report: https://bugzilla.redhat.com/show_bug.cgi?id=2101963

[pllim]

Hmm lots of cosmology in there… @nstarman ?

Though ultimately, this is hard to fix until we update CI to test against Python 3.11. Maybe soon… I just noticed RC1 is out. https://docs.python.org/3.11/whatsnew/3.11.html

[pllim]

@sergiopasra , please try again with latest dev astropy. Should be fixed now. Thanks for your patience!