This updates _PyErr_ChainStackItem() to use _PyErr_SetObject()
instead of _PyErr_ChainExceptions(). This prevents a hang in
certain circumstances because _PyErr_SetObject() performs checks
to prevent cycles in the exception context chain while
_PyErr_ChainExceptions() doesn't.
When an asyncio.Task is cancelled, the exception traceback now
starts with where the task was first interrupted. Previously,
the traceback only had "depth one."
bpo-3605, bpo-38733: Optimize _PyErr_Occurred(): remove "tstate ==
NULL" test.
Py_FatalError() no longer calls PyErr_Occurred() if called without
holding the GIL. So PyErr_Occurred() no longer has to support
tstate==NULL case.
_Py_CheckFunctionResult(): use directly _PyErr_Occurred() to avoid
explicit "!= NULL" test.
* Replace global var Py_VerboseFlag with interp->config.verbose.
* Add _PyErr_NoMemory(tstate) function.
* Add tstate parameter to _PyEval_SetCoroutineOriginTrackingDepth()
and move the function to the internal API.
* Replace _PySys_InitMain(runtime, interp)
with _PySys_InitMain(runtime, tstate).