Tkinter widgets to work in wantobjects=True mode.

OSError(22, 'Invalid argument') when writing input data into stdin, whereas
the process already exited.

and to modernize.  Patch by Gareth Rees.

Patch based on lines from Georg Brandl, Eric Snow, and Gareth Rees.

Replace it with correct logic that raises ValueError for bad input.
Issues #8478 and #12691 reported the incorrect logic.
Add an Untokenize test case and an initial test method.

Patch by Vajrasky Kok.

variables names and values.

Based on patch by Stephen Tu.

This silences a Coverity complain.

to the internal Mac/README file.

on Windows if source name ends with os.altsep.

_active shouldn't be cached, it set to None on shutdown.

This is more RFC compliant (see issue) and fixes a problem with
signature verifiers rejecting the part when signed.  There is some
amount of backward compatibility concern here since it changes
the output, but the RFC issue coupled with fixing the problem
with signature verifiers seems worth the small risk of breaking
code that depends on the current incorrect output.

Addressing #issue 20529

Issue #20540: Fix a performance regression (vs. Python 3.2) when layering a multiprocessing Connection over a TCP socket.
For small payloads, Nagle's algorithm would introduce idle delays before the entire transmission of a message.