Fix the following warning:

Python/pystrtod.c: In function 'format_float_short':
Python/pystrtod.c:1007:13: warning: 'strncpy' output truncated before terminating nul copying 3 bytes from a string of the same length [-Wstringop-truncation]
             strncpy(p, "ERR", 3);

(cherry picked from commit 9fb84157)

(cherry picked from commit e0e5065d)
Co-authored-by: Serhiy Storchaka <storchaka@gmail.com>

This makes streamed zips compatible with MacOS Archive Utility and
other applications.
(cherry picked from commit 4ba3b50b)
Co-authored-by: Silas Sewell <silas@sewell.org>

Also make docs for NEWFALSE and NEWTRUE more consistent
with docs for other opcodes.
(cherry picked from commit 488cfb78)
Co-authored-by: Krzysztof Wroblewski <krzysiek.wr@gmail.com>

https://bugs.python.org/issue34623
(cherry picked from commit 026337a7)
Co-authored-by: Christian Heimes <christian@python.org>


https://bugs.python.org/issue34623

(cherry picked from commit 8213eadd)
Co-authored-by: Berker Peksag <berker.peksag@gmail.com>

Update all test certs and keys to use future proof crypto settings:

* 3072 bit RSA keys
* SHA-256 signature

Signed-off-by: Christian Heimes <christian@python.org>.
(cherry picked from commit e6dac007)



https://bugs.python.org/issue34542

Co-authored-by: Vladimir Matveev <v2matveev@outlook.com>

(cherry picked from commit 9bdb7be4)

The C accelerated _elementtree module now initializes hash randomization
salt from _Py_HashSecret instead of libexpat's default CPRNG.
Signed-off-by: Christian Heimes <christian@python.org>

https://bugs.python.org/issue34623.
(cherry picked from commit cb5778f0)
Co-authored-by: Christian Heimes <christian@python.org>



https://bugs.python.org/issue34623

Include ``openssl/dh.h`` header file to fix implicit function declaration of ``DH_free()``.

Signed-off-by: Alexandru Ardelean <ardeleanalex@gmail.com>.
(cherry picked from commit b3a271fc)
Co-authored-by: Alexandru Ardelean <ardeleanalex@gmail.com>



https://bugs.python.org/issue34710

(cherry picked from commit 76aa2c0a9a8dd3ac90b91e7342c8ce8125bf21f9)
Co-authored-by: larryhastings <larry@hastings.org>

(cherry picked from commit 3fe33043)



https://bugs.python.org/issue19417

When the server has closed the connection before sending a status-line,
the client's error message should have a more descriptive error message

https://bugs.python.org/issue8450


https://bugs.python.org/issue8450

(cherry picked from commit a4414ef2)

It was accidentally added in 107f3cc7.

(cherry picked from commit a710ebd2)

(cherry picked from commit 40caa05f)
Co-authored-by: Benjamin Peterson <benjamin@python.org>

Reported by Svace static analyzer.
(cherry picked from commit 6f82bffd)
Co-authored-by: Alexey Izbyshev <izbyshev@ispras.ru>

It was backported in 0cc43df0.

(cherry picked from commit b9bf9d02)
Co-authored-by: Benjamin Peterson <benjamin@python.org>

https://bugs.python.org/issue34405

(cherry picked from commit 31912b43c903aafad09350899ed6a9dec7c43421)
Co-authored-by: Ned Deily <nad@python.org>

<!-- issue-number: [bpo-34405](https://www.bugs.python.org/issue34405) -->
https://bugs.python.org/issue34405
<!-- /issue-number -->

(cherry picked from commit 6b273f7f)
Co-authored-by: Bo Bayles <bbayles@gmail.com>

[2.7] closes bpo-31608: Fix a crash in methods of a subclass of _collections.deque with a bad __new__(). (GH-9179)

(cherry picked from commit 5033aa77)
Co-authored-by: Benjamin Peterson <benjamin@python.org>

Python 2 never checked for I/O error when reading .py files and
thus could mistake an I/O error for EOF and create incorrect .pyc
files.
This adds an check for this and aborts on an error.

Many type object initializations labeled a field "tp_size" in the
comment, but the name of that field is tp_basicsize..
(cherry picked from commit 0e0bc4e2)
Co-authored-by: Peter Eisentraut <peter@eisentraut.org>

(cherry picked from commit 4e519377)
Co-authored-by: Zackery Spytz <zspytz@gmail.com>

When calling tp_descr_get(self, obj, type), make sure that
we own a strong reference to "self".

(cherry picked from commit 8f735485)

(cherry picked from commit 7d81e8f5)
Co-authored-by: Serhiy Storchaka <storchaka@gmail.com>

distutils.spawn.find_executable() now falls back on os.defpath if the
PATH environment variable is not set.

(cherry picked from commit 39487196)

The change to Tools/scripts/diff.py effectively backports part of
a2637729.
The test code changed in Doc/library/difflib.rst is not present in current 3.x.

... by removing a superfluous "either".

Reported by Никита Люшненко on docs@

(cherry picked from commit 98b976a2)

Sometimes some versions of the shared libraries that are part of the
traceback are compiled in optimised mode and the Program Counter (PC)
is not present, not allowing gdb to walk the frames back. When this
happens, the Python bindings of gdb raise an exception, making the
test impossible to succeed.
(cherry picked from commit f2ef51f8)
Co-authored-by: Pablo Galindo <Pablogsal@gmail.com>

closes bpo-34540: Convert shutil._call_external_zip to use subprocess rather than distutils.spawn. (GH-8985)

(cherry picked from commit 91cb298f)
Co-authored-by: Vladimir Matveev <v2matveev@outlook.com>

(cherry picked from commit 704e2d37)
Co-authored-by: Christian Heimes <christian@cheimes.de>