Modify RE examples in documentation to use raw strings to prevent DeprecationWarning.
Add text to REGEX HOWTO to highlight the deprecation.  Approved by Serhiy Storchaka.

* Make sure ``__spec__.loader`` matches ``__loader__`` for namespace packages.
* Make sure ``__spec__.origin` matches ``__file__`` for namespace packages.

https://bugs.python.org/issue32303
https://bugs.python.org/issue32305

This reverts commit 72a0d218.

The reverted commit had a few issues so it was unanimously decided
to undo it. See the bpo issue for details.

Clarify that the level argument is used to determine whether to
perform absolute or relative imports: 0 is absolute, while a positive number
is the number of parent directories to search relative to the current module.

* bpo-32711: Fix warnings for Python/ast_unparse.c

It was deprecated in 3.6.

In the tutorial about the Generator expression, there is an example with
a dict comprehension and not with a generator expression, just removed
the code.

The f-string example for using datetime format specifier does not match the given output.
Changed the format from %b to %B so it matches the output of "January".

Mention only ImportError caused by importing sitecustomize.py/usercustomize.py
themselves will be silently ignored.

When using customized decode error handlers, it is possible for builtin decoders
to write out-of-bounds and then crash.

tarfile and zipfile now sort directory listing to generate tar and zip archives
in a more reproducible way.

See also https://reproducible-builds.org/docs/stable-inputs/ on that topic.

Do not pass the name field in the 'from' address in the SMTP envelope.

This issue covers various changes for the macOS installers provided via python.org for 3.7.0.

- Provide a provisional new installer variant for macOS 10.9 and later systems with 64-bit (x86_64) architecture only.  Apple has made it known that future versions of macOS will only fully support 64-bit executables and some other third-party software suppliers have chosen 10.9 as their oldest supported system.
 
- Support **Tcl/Tk 8.6** with the 10.9 installer variant.
 
- Upgrade **OpenSSL** to 1.1.0g and **SQLite** to 3.22.0.
 
- The compiler name used for the interpreter build and for modules built with **Distutils / pip** is now _gcc_ rather than _gcc-4.2_. And extension module builds will no longer try to force use of an old SDK if present.

EPOLL_CLOEXEC is not defined on Android.
Co-Authored-By: Wataru Matsumoto <sxsns243@gmail.com>

No longer add /Library/Python/3.x/site-packages, the Apple-supplied
system Python site-packages directory, to sys.path for macOS framework
builds in case Apple ships a version of Python 3. A similar change
was made earlier to Python 2.7 where it was found that the coupling
between the system Python and a user-installed framework Python often
caused confusion or pip install failures.

Some commands are specified in the documentation, but there is no direct
references.

This allows for nested zip files, tar files within zip files, zip files within tar files, etc.

Contributed by: John Jolly

Band-aid for macOS: Some platforms seem to ignore unknown protocols.
Signed-off-by: Christian Heimes <christian@python.org>

Allow os.PathLike args in subprocess APIs.

Fix two (in my opinion) spurious failure conditions in the lib2to3.tests.test_parser.TestParserIdempotency test_parser test.

    Use the same encoding found in the initial file to write a temp file for a diff. This retains the BOM if the encoding was initially utf-8-sig.

    If the file cannot be parsed using the normal grammar, try again with no print statement which should succeed for valid files using future print_function

For case (1), the driver was correctly handling a BOM in a utf-8 file, but then the test was not writing a comparison file using 'utf-8-sig' to diff against, so the BOM got removed. I don't think that is the fault of the parser, and lib2to3 will retain the BOM.

For case (2), lib2to3 pre-detects the use of from __future__ import print_function or allows the user to force this interpretation with a -p flag, and then selects a different grammar with the print statement removed. That makes the test cases unfair to this test as the driver itself doesn't know which grammar to use. As a minimal fix, the test will try using a grammar with the print statement, and if that fails fall back on a grammar without it. A more thorough handling of the idempotency test would to be to parse all files using both grammars and ignore if one of the two failed but otherwise check both. I didn't think this was necessary but can change.

Add "capture_output=True" option to subprocess.run, this is equivalent to
setting stdout=PIPE, stderr=PIPE but is much more readable.

See https://bugs.python.org/issue32441 for where this was introduced.

This allows the compression level to be specified when writing zipfiles
(for the entire file *and* overridden on a per-file basis).

Contributed by Bo Bayles

Do not allow receiving a SIGINT to cause the subprocess module to trigger an
immediate SIGKILL of the child process.  SIGINT is normally sent to all child
processes by the OS at the same time already as was the established normal
behavior in 2.7 and 3.2.  This behavior change was introduced during the fix to https://bugs.python.org/issue12494 and is generally surprising to command line
tool users who expect other tools launched in child processes to get their own
SIGINT and do their own cleanup.

In Python 3.3-3.6 subprocess.call and subprocess.run would immediately
SIGKILL the child process upon receiving a SIGINT (which raises a
KeyboardInterrupt).  We now give the child a small amount of time to
exit gracefully before resorting to a SIGKILL.

This is also the case for subprocess.Popen.__exit__ which would
previously block indefinitely waiting for the child to die.  This was
hidden from many users by virtue of subprocess.call and subprocess.run
sending the signal immediately.

Behavior change: subprocess.Popen.__exit__ will not block indefinitely
when the exiting exception is a KeyboardInterrupt.  This is done for
user friendliness as people expect their ^C to actually happen.  This
could cause occasional orphaned Popen objects when not using `call` or
`run` with a child process that hasn't exited.

Refactoring involved: The Popen.wait method deals with the
KeyboardInterrupt second chance, existing platform specific internals
have been renamed to _wait().
Also fixes comment typos.