This reverts commit e38d12ed.

* Maintain a list of BufferedWriter objects.  Flush them on exit.

In Python 3, the buffer and the underlying file object are separate
and so the order in which objects are finalized matters.  This is
unlike Python 2 where the file and buffer were a single object and
finalization was done for both at the same time.  In Python 3, if
the file is finalized and closed before the buffer then the data in
the buffer is lost.

This change adds a doubly linked list of open file buffers.  An atexit
hook ensures they are flushed before proceeding with interpreter
shutdown.  This is addition does not remove the need to properly close
files as there are other reasons why buffered data could get lost during
finalization.

Initial patch by Armin Rigo.

* Use weakref.WeakSet instead of WeakKeyDictionary.

* Simplify buffered double-linked list types.

* In _flush_all_writers(), suppress errors from flush().

* Remove NEWS entry, use blurb.

* Fix terminology in comment and add more design rationale.

* Fix extra space

In Python 3.6, sorted() was removed from _make_key() for the lru_cache and instead rely on guaranteed keyword argument order preservation.  This makes keyword argument handling faster but it also causes multiple callers with a different keyword argument order to be cached as separate items.  Depending on your point of view, this is either a performance regression (increased number of cache misses) or a performance enhancement (faster computation of keys).

* bpo-31170: Update libexpat from 2.2.3 to 2.2.4

Fix copying of partial characters for UTF-8 input (libexpat bug 115):
https://github.com/libexpat/libexpat/issues/115

* Add NEWS entry.

sys.modules is the one true source.

See PEP 11.

Broken in GH-2079

* Change NPN detection:

Version breakdown, support disabled (pre-patch/post-patch):
- pre-1.0.1: OPENSSL_NPN_NEGOTIATED will not be defined -> False/False
- 1.0.1 and 1.0.2: OPENSSL_NPN_NEGOTIATED will not be defined ->
False/False
- 1.1.0+: OPENSSL_NPN_NEGOTIATED will be defined and
OPENSSL_NO_NEXTPROTONEG will be defined -> True/False

Version breakdown support enabled (pre-patch/post-patch):
- pre-1.0.1: OPENSSL_NPN_NEGOTIATED will not be defined -> False/False
- 1.0.1 and 1.0.2: OPENSSL_NPN_NEGOTIATED will be defined and
OPENSSL_NO_NEXTPROTONEG will not be defined -> True/True
- 1.1.0+: OPENSSL_NPN_NEGOTIATED will be defined and
OPENSSL_NO_NEXTPROTONEG will not be defined -> True/True

* Refine NPN guard:

- If NPN is disabled, but ALPN is available we need our callback
- Make clinic's ssl behave the same way

This created a working ssl module for me, with NPN disabled and ALPN
enabled for OpenSSL 1.1.0f.

Concerns to address:
The initial commit for NPN support into OpenSSL [1], had the
OPENSSL_NPN_* variables defined inside the OPENSSL_NO_NEXTPROTONEG
guard. The question is if that ever made it into a release.
This would need an ugly hack, something like:

	#if defined(OPENSSL_NO_NEXTPROTONEG) && \
		!defined(OPENSSL_NPN_NEGOTIATED)
	#	define OPENSSL_NPN_UNSUPPORTED 0
	#	define OPENSSL_NPN_NEGOTIATED 1
	#	define OPENSSL_NPN_NO_OVERLAP 2
	#endif

[1] https://github.com/openssl/openssl/commit/68b33cc5c7

This comment hasn't been true since Python 3.0.

* bpo-1198569: Allow the braced pattern to be different

``string.Template`` subclasses can optionally define ``braceidpattern`` if
they want to specify different placeholder patterns inside and outside the
braces.  If None (the default) it falls back to ``idpattern``.

Blurbify master branch.

Signed-off-by: Christian Heimes <christian@python.org>

Patch by Paul.j3.  Includes an unrelated but useful addition to the
optparse porting section.

* Change code owners for hashlib and ssl to the crypto team

* Include the core CSPRNG for the crypto-team

Fix fileinput with inplace=True to accept pathlib.Path objects.

We never actually check HAVE_SELECT.

This is a required feature is C99, which we require.

Used in macOS framework builds.

Store exceptions as string rather than object to prevent reference
cycles which cause leaking dangling threads.

Call doCleanups() to close the loop after calling
executor.shutdown(wait=True): see TestCase.set_event_loop() of
asyncio.test_utils.

Replace also gc.collect() with support.gc_collect().

* bpo-31326: ProcessPoolExecutor waits for the call queue thread

concurrent.futures.ProcessPoolExecutor.shutdown() now explicitly
closes the call queue. Moreover, shutdown(wait=True) now also join
the call queue thread, to prevent leaking a dangling thread.

* Fix for shutdown() being called twice.

bpo-27144: concurrent.futures as_complete and map iterators do not keep reference to returned object (#1560)

* bpo-27144: concurrent.futures as_complie and map iterators do not keep
reference to returned object

* Some nits.  Improve wordings in docstrings and comments, and avoid relying on
sys.getrefcount() in tests.