Fix showing SystemExit exception raise inside except handler (#14503) Doing something like this: ```python try: 5 / 0 except Exception as e: raise SystemExit ``` was hitting an error inside UltraTB, creating a long traceback of its internals (which, ironically, UltraTB itself then displays correctly :-). `ListTB.get_exception_only()` calls the `ListTB.structured_traceback()` method *specifically* - even if `self` is a subclass, it won't use the subclass's method. However, the exception chaining in that method uses recursion by calling `self.structured_traceback()`, which will use a subclass's method. Tuples were added as an option there to support exception chaining, but not all of the machinery in connected classes expects a tuple. This just skips the exception chaining logic for the `etb=None` case, when we're showing the exception only. I'm not sure this is necessarily the best fix, but I didn't want to spend too much time following code around a module that's old enough to vote. Closes #12104

Fix some tests on Python 3.13 RC1 (#14504) Random little odds and ends that have changed in 3.13 break the tests. I think this should get the CI working again. :crossed_fingers: Closes #14457 Closes #14458

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Relax string checks in test_pinfo_docstring_dynamic Allows this test to pass on Python 3.13

Fix test_decorator_skip_with_breakpoint() on Python 3.13

Fix test_ipdb_magics doctest for Python 3.13

Fix showing SystemExit exception raise inside except handler

Only copy files in startup dir if we just created it. (#14497) Closes #14496

Apply suggestions from code review Co-authored-by: James Beith <james@beith.co.uk>

Only copy files in startup dir if we just created it. Closes #14496