830daae1 added some new GIL-releasing to new_buffersize. This is fine, but it's better to avoid reacquiring the GIL for as long as possible. Also, it should use FILE_(BEGIN|END)_ALLOW_THREADS to avoid having the file closed from under it.

Multiple threads iterating over a file can corrupt the file's internal readahead
buffer resulting in crashes. To fix this, cache buffer state thread-locally for
the duration of a file_iternext call and only update the file's internal state
after reading completes.

No attempt is made to define or provide "reasonable" semantics for iterating
over a file on multiple threads. (Non-crashing) races are still
present. Duplicated, corrupt, and missing data will happen.

This was originally fixed by 6401e567, which
raised an exception from seek() and next() when concurrent operations were
detected. Alas, this simpler solution breaks legitimate use cases such as
capturing the standard streams when multiple threads are logging.

Updates documentation for generator expressions in classes tutorial: Clarify usage of ambiguous term "brackets" by replacing with "square brackets". Updated subsequent lines to respect line breaks. (GH-5079)
(cherry picked from commit f190eb59)

(cherry picked from commit 7cc42c35)

Move other test to more proper place.
(cherry picked from commit e8ed9655)

(cherry picked from commit fe90efdc07ec70fd4ff28eac179448a41379cff1)

select.error doesn't have an errno attribute so access the errno by
indexing instead.

(cherry picked from commit e3256087)

(cherry picked from commit e5f7dcce)

(cherry picked from commit 53f91356)

(cherry picked from commit d11e8e0d)

This is more complicated than it should be because we need to preserve the
useful mtime-based regeneration feature that lib2to3.pgen2.driver.load_grammar
has. We only look for the pickled grammar file with pkgutil.get_data and only if
the source file does not exist..
(cherry picked from commit 8a587716)

(cherry picked from commit 83cb778b)

(cherry picked from commit 4f29f3c8)

(cherry picked from commit b748e3b2)

netrc file format doesn't support quotes and escapes.

See https://linux.die.net/man/5/netrc

bpo-32212: Updated logging documentation to make parameter names more consistent with source. (GH-4765) (GH-4768)

(cherry picked from commit a9f8df64)

In fileio, there were 3 fstat() calls and one lseek() call that did not
release the GIL during the call. This can cause all threads to hang for
unlimited time when using io.FileIO with inaccessible NFS server.

Same issue seen in fileio exists also in fileobject, fixed in the same
way.

(cherry picked from commit ae342cf7)

[2.7] bpo-10544: Deprecate "yield" in comprehensions and generator expressions in Py3k mode. (GH-4579) (#4676)

When PyGILState_Ensure() is called in a non-Python thread before
PyEval_InitThreads(), only call PyEval_InitThreads() after calling
PyThreadState_New() to fix a crash.

(cherry picked from commit b4d1e1f7)

Avoid also "cd $(srcdir)" to not change the current directory.

(cherry picked from commit 3be3b97a)

Remove a flakey test and rewrite another one for readability.

(cherry picked from commit cc55e78a)

characters/bytes for non-negative n.  This makes it compatible with
read() methods of other file-like objects.
(cherry picked from commit 219c2de5)

(cherry picked from commit afd055a5)

Mention that the lower the priority number, the higher priority it represents.
(cherry picked from commit 9d5ec808)

The provided code example was supposed to find repeated words, however it returned false results.
(cherry picked from commit 610e5afd)

The paragraph that contains example of string literal concatenation was placed
after the section about concatenation using the '+' sign.
Moved the paragraph to the appropriate section.
(cherry picked from commit 78a5722a)

Move footnote markers to be closer to the related terminology:
before the end of the sentence, instead of after.
(cherry picked from commit cdfe910e)

_PyObject_DebugReallocApi() now calls Py_FatalError() if realloc()
fails to shrink a memory block.

Call Py_FatalError() because _PyObject_DebugReallocApi() erased freed
bytes *before* realloc(), expecting that realloc() *cannot* fail to
shrink a memory block.

* bpo-31324: Optimize support._match_test() (#4421)

* Rename support._match_test() to support.match_test(): make it
  public
* Remove support.match_tests global variable. It is replaced with a
  new support.set_match_tests() function, so match_test() doesn't
  have to check each time if patterns were modified.
* Rewrite match_test(): use different code paths depending on the
  kind of patterns for best performances.
Co-Authored-By: Serhiy Storchaka <storchaka@gmail.com>
(cherry picked from commit 803ddd8c)

* bpo-31324: Fix test.support.set_match_tests(None) (#4505)

(cherry picked from commit bb11c3c9)
(cherry picked from commit 70b2f8797146a56a6880743424f0bedf4fc30c62)

Fix the following warning:

Warning -- files was modified by test_builtin
  Before: []
  After:  ['@test_19422_tmp']
1 test altered the execution environment:
    test_builtin

Replace python3 with python2.

The line number in correct when using the -x option: Py_Main() uses
ungetc() to not skip the first newline character.

(cherry picked from commit 7750bded)

`kargs` -> `kwargs`