(cherry picked from commit f4ea642c)

[2.7] bpo-31285: Don't raise a SystemError in warnings.warn_explicit() in case __loader__.get_source() has a bad splitlines() method. (GH-3219) (#3823)

(cherry picked from commit 91fb0afe)

* init commit, with initial tests for from_param and fields __set__ and __get__, and some additions to from_buffer and from_buffer_copy

* added the rest of tests and patches. probably only a first draft.

* removed trailing spaces

* replace ctype with ctypes in error messages

* change back from ctypes instance to ctype instance

(cherry picked from commit 1bea762d)

[2.7] bpo-31490: Fix an assertion failure in ctypes in case an _anonymous_ attr is defined only outside _fields_. (GH-3615) (#3780)

(cherry picked from commit 30b61b51)

[2.7] bpo-31311: Fix a SystemError and a crash in ctypes._CData.__setstate__(), in case of a bad __dict__. (GH-3254). (#3781)

(cherry picked from commit 57c2561c)

(cherry picked from commit d6238a76)

[2.7] bpo-30347: Stop crashes when concurrently iterate over itertools.groupby() iterators. (GH-1557). (#3772)

(cherry picked from commit c740e4fe)

(cherry picked from commit 0e950dd2)

Patch by Raymond Hettinger.

Non-regression tests for the Expat 2.2.3 UTF-8 decoder bug.

(cherry picked from commit e6d9fcbb)

Previously ensurepip would always report success, even if the
pip installation failed.

(cherry picked from commit 9adda0cd)

Use prefixed macro names for the `authoraddress` function, add T2A to the font encoding in LaTeX sources to support Cyrillic characters in the PDF documentation, and replace the deprecated `font_size` config option with `pointsize`.
(cherry picked from commit da9b4cfb)

(cherry picked from commit 19e4d934)

(cherry picked from commit da67e0d6)

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

[2.7] bpo-31471: Fix assertion failure in subprocess.Popen() on Windows, in case env has a bad keys() method. (GH-3580) (#3595)

This no-op change makes 2.7 more consistent with 3.x to ease comparison and backports.

(cherry picked from commit 1de4705d)

fork_wait.py tests now joins threads, to not leak running threads in
the background.

(cherry picked from commit c99d41f9)

(cherry picked from commit 71fe8c00)

[2.7] bpo-31411: Prevent raising a SystemError in case warnings.onceregistry is not a dictionary. (GH-3485). (#3493)

(cherry picked from commit 252033d5)

(cherry picked from commit 2e6bb448)

ttk.OptionMenu radiobuttons weren't unique 
between instances of OptionMenu.
(cherry picked from commit a568e527)

Patch by Paul.j3.  Includes an unrelated but useful addition to the
optparse porting section.
(cherry picked from commit 0c7983e4)

* bpo-29136: Add TLS 1.3 support

TLS 1.3 introduces a new, distinct set of cipher suites. The TLS 1.3
cipher suites don't overlap with cipher suites from TLS 1.2 and earlier.
Since Python sets its own set of permitted ciphers, TLS 1.3 handshake
will fail as soon as OpenSSL 1.1.1 is released. Let's enable the common
AES-GCM and ChaCha20 suites.

Additionally the flag OP_NO_TLSv1_3 is added. It defaults to 0 (no op) with
OpenSSL prior to 1.1.1. This allows applications to opt-out from TLS 1.3
now.

Signed-off-by: Christian Heimes <christian@python.org>.
(cherry picked from commit cb5b68ab)

Signed-off-by: Christian Heimes <christian@python.org>
(cherry picked from commit 17c9ac92)

Also provide a solution if the user wants to keep multiple blank lines.
(cherry picked from commit 397c467c)

See also 1f29cefc.  The configure.ac change was omitted from the earlier change...

Signed-off-by: Christian Heimes <christian@python.org>.
(cherry picked from commit d3b9f97e)

Signed-off-by: Christian Heimes <christian@python.org>
(cherry picked from commit ad0ffa03)

(cherry picked from commit 8204b903)

This also eliminats a dead link to Weave in the process..
(cherry picked from commit 78ffd6cf)