bpo-36829: Add sys.unraisablehook() by vstinner · Pull Request #13187 · python/cpython

Add new sys.unraisablehook() function which can be overriden to
control how "unraisable exceptions" are handled. It is called when an
exception has occurred but there is no way for Python to handle it.
For example, when a destructor raises an exception or during garbage
collection (gc.collect()).

Changes:

* The default hook now ignores exception on writing the traceback.
* Add an internal UnraisableHookArgs type used to pass arguments to
  sys.unraisablehook.
* Add _PyErr_WriteUnraisableDefaultHook().
* test_sys now uses unittest.main() to automatically discover tests:
  remove test_main().
* Add _PyErr_Init().
* Fix PyErr_WriteUnraisable(): hold a strong reference to sys.stderr
  while using it