exception raised by sys.exit is None when no code is given.

As suggested by Serhiy Storchaka.

and to modernize.  Patch by Gareth Rees.

no parameter

crash when a generator is created in a C thread that is destroyed while the
generator is still used. The issue was that a generator contains a frame, and
the frame kept a reference to the Python state of the destroyed C thread. The
crash occurs when a trace function is setup.

Python now uses SipHash24 on all major platforms.

Issue #18948: improve SuppressCoreFiles to include Windows crash popup suppression, and use it in more tests.
Patch by Valerie Lambert and Zachary Ware.

Issue #19087: Improve bytearray allocation in order to allow cheap popping of data at the front (slice deletion).

error messages and comments.

 -I

    Run Python in isolated mode. This also implies -E and -s. In isolated mode
    sys.path contains neither the script’s directory nor the user’s
    site-packages directory. All PYTHON* environment variables are ignored,
    too. Further restrictions may be imposed to prevent the user from
    injecting malicious code.

Issue #17934: Add a clear() method to frame objects, to help clean up expensive details (local variables) and break reference cycles.

Issue #18214: Improve finalization of Python modules to avoid setting their globals to None, in most cases.

(Issue #17807: Generators can now be finalized even when they are part of a reference cycle)

Following issue #13390, fix compilation --without-pymalloc, and make sys.getallocatedblocks() return 0 in that situation.

Issue #13390: New function :func:`sys.getallocatedblocks()` returns the number of memory blocks currently allocated.
Also, the ``-R`` option to regrtest uses this function to guard against memory allocation leaks.

Patch from Serhiy Storchaka.

Patch by Serhiy Storchaka.

Patch by Serhiy Storchaka.

Patch by Serhiy Storchaka.

Issue 14673: Add sys.implementation

This replaces the original PEP 409 implementation. See #14133.