* bpo-36402: Fix threading._shutdown() race condition (GH-13948)
Fix a race condition at Python shutdown when waiting for threads.
Wait until the Python thread state of all non-daemon threads get
deleted (join all non-daemon threads), rather than just wait until
Python threads complete.
* Add threading._shutdown_locks: set of Thread._tstate_lock locks
of non-daemon threads used by _shutdown() to wait until all Python
thread states get deleted. See Thread._set_tstate_lock().
* Add also threading._shutdown_locks_lock to protect access to
threading._shutdown_locks.
* Add test_finalization_shutdown() test.
(cherry picked from commit 468e5fec8a)
* bpo-36402: Fix threading.Thread._stop() (GH-14047)
Remove the _tstate_lock from _shutdown_locks, don't remove None.
(cherry picked from commit 6f75c87375)
Add a new threading.excepthook() function which handles uncaught
Thread.run() exception. It can be overridden to control how uncaught
exceptions are handled.
threading.ExceptHookArgs is not documented on purpose: it should not
be used directly.
* threading.excepthook() and threading.ExceptHookArgs.
* Add _PyErr_Display(): similar to PyErr_Display(), but accept a
'file' parameter.
* Add _thread._excepthook(): C implementation of the exception hook
calling _PyErr_Display().
* Add _thread._ExceptHookArgs: structseq type.
* Add threading._invoke_excepthook_wrapper() which handles the gory
details to ensure that everything remains alive during Python
shutdown.
* Add unit tests.
* bpo-6532: Make the thread id an unsigned integer.
From C API side the type of results of PyThread_start_new_thread() and
PyThread_get_thread_ident(), the id parameter of
PyThreadState_SetAsyncExc(), and the thread_id field of PyThreadState
changed from "long" to "unsigned long".
* Restore a check in thread_get_ident().
