Python 3.15 compatibility

[frenzymadness]

There are some failing tests when run with Python 3.15 alpha 6:

FAILED test/test_api/test_interpreter.py::test__getattr__completions[False-False] - AssertionError: assert [] == ['fbar', 'foo']
FAILED test/test_api/test_interpreter.py::test__getattr__completions[False-True] - AssertionError: assert [] == ['fbar', 'foo']
FAILED test/test_api/test_interpreter.py::test_property_error_oldstyle[False] - AssertionError: assert [] == ['bar']
FAILED test/test_api/test_interpreter.py::test_property_error_newstyle[False] - AssertionError: assert [] == ['bar']
FAILED test/test_api/test_interpreter.py::test_dir_magic_method[False] - AssertionError: assert ('__dir__' in []) is True
FAILED test/test_api/test_interpreter.py::test_dunders[False-DunderCls()[0]-int-False] - ValueError: not enough values to unpack (expected 1, got 0)
FAILED test/test_api/test_interpreter.py::test_dunders[False-DunderCls()[0]-int-True] - ValueError: not enough values to unpack (expected 1, got 0)
FAILED test/test_api/test_interpreter.py::test_dunders[False-dunder[0]-int-False] - ValueError: not enough values to unpack (expected 1, got 0)
FAILED test/test_api/test_interpreter.py::test_dunders[False-dunder[0]-int-True] - ValueError: not enough values to unpack (expected 1, got 0)
FAILED test/test_api/test_interpreter.py::test_dunders[False-next(DunderCls())-float-False] - ValueError: not enough values to unpack (expected 1, got 0)
FAILED test/test_api/test_interpreter.py::test_dunders[False-next(DunderCls())-float-True] - ValueError: not enough values to unpack (expected 1, got 0)
FAILED test/test_api/test_interpreter.py::test_dunders[False-next(dunder)-float-False] - ValueError: not enough values to unpack (expected 1, got 0)
FAILED test/test_api/test_interpreter.py::test_dunders[False-next(dunder)-float-True] - ValueError: not enough values to unpack (expected 1, got 0)
FAILED test/test_api/test_interpreter.py::test_dunders[False-for x in DunderCls(): x-str-False] - ValueError: not enough values to unpack (expected 1, got 0)
FAILED test/test_api/test_interpreter.py::test_dunders[False-for x in DunderCls(): x-str-True] - ValueError: not enough values to unpack (expected 1, got 0)
FAILED test/test_api/test_interpreter.py::test_param_infer_default - AssertionError: assert 'number' == 'x'
FAILED test/test_api/test_interpreter.py::test_custom__getitem__[False-True] - AssertionError: assert [] == ['upper']
FAILED test/test_utils.py::TestSetupReadline::test_import - AssertionError: assert 57 < 40

I already have fix for this, but I'd like to finish #2064 via #2093 first, reporting just for awareness.