chore: update framework tests to pass under Python 3.12

[tonyandrewmeyer]

The behaviour of descriptors changed in 3.12, so that when __set_name__ raises an exception, that exception reaches the code that did the name setting, with a note attached, unlike earlier Python where the exception was chained.

Minimal code

import sys
print(sys.version)
class Foo:
    def __init__(self):
        self.name = None
    def __set_name__(self, owner, name):
        if self.name is not None:
            raise RuntimeError("hello world!")
        self.name = name

f = Foo()
class A:
    x = f
try:
    class B:
        x = f
except Exception as e:
    if hasattr(e, "__notes__"):
        print(f"notes: {e.__notes__!r}")
    print(f"cause: {e.__cause__!r}")
    print(f"context: {e.__context__!r}")
    print(f"str: {e}")

Python 3.11

3.11.5 (main, Oct  2 2023, 11:58:32) [GCC 11.4.0]
cause: RuntimeError('hello world!')
context: RuntimeError('hello world!')
str: Error calling __set_name__ on 'Foo' instance 'x' in 'B'

Python 3.12

3.12.0 (main, Oct  3 2023, 10:11:00) [GCC 11.4.0]
notes: ["Error calling __set_name__ on 'Foo' instance 'x' in 'B'"]
cause: None
context: None
str: hello world!

In the framework tests, we verify that the event source is not being reused by checking the str of the causing exception, but that doesn't work in both 3.12 and earlier Python because of this Python change.

I couldn't find a way to use exactly the same code in Python 3.12 and earlier, so have checked for the presence of the __notes__ attribute - if it is there, then the "Error calling set_name" piece will be in in the notes, and so we look at the exception itself; if it is not there, then we assume the earlier behaviour and look at the causing exception. This could be a check against sys.version_info instead if that was preferred.

[benhoyt]

Thanks!