Based on the investigation by Xiang Zhang.

References could leak, NULL could be dereferenced, and the Expat parser could
be double freed when some errors raised.

_PyObject_Dump() now uses an heuristic to check if the object memory
has been freed: log "<freed object>" in that case.

The heuristic rely on the debug hooks on Python memory allocators
which fills the memory with DEADBYTE (0xDB) when memory is
deallocated. Use PYTHONMALLOC=debug to always enable these debug
hooks.

Fix the documentation of copy2, as it does not copy file ownership (user and
group), only mode, mtime, atime and flags.

The original text was confusing to developers as it suggested that this
command is the same as 'cp -p', but according to cp(1), '-p' copies file
ownership as well.

Clarify which metadata is copied by shutil.copystat in its docstring.

https://bugs.python.org/issue35028

* Use _PyUnicode_Copy in sanitize_isoformat_str

* Use repr in fromisoformat error message

This reverses commit 67b74a98b2 per Serhiy Storchaka's suggestion:

     I suggested to use %R in the error message because including the raw
     string can be confusing in the case of empty string, or string
     containing trailing whitespaces, invisible or unprintable characters.

We agree that it is better to change both the C and pure Python versions
to use repr.

* Retain non-sanitized dtstr for error printing

This does not create an extra string, it just holds on to a reference to
the original input string for purposes of creating the error message.

* PEP 7 fixes to from_isoformat

* Separate handling of Unicode and other errors

In the initial implementation, errors other than encoding errors would
both raise an error indicating an invalid format, which would not be
true for errors like MemoryError.

* Drop needs_decref from _sanitize_isoformat_str

Instead _sanitize_isoformat_str returns a new reference, even to the
original string.

The assignment of i/2 to nk is redundant because on this code path, nk is already the size of the dictionary, and i is already twice the size of the dictionary. I've replaced the store with an assertion that i/2 is nk.

Raise ValueError OverflowError in case of a negative
_length_ in a ctypes.Array subclass.  Also raise TypeError
instead of AttributeError for non-integer _length_.
Co-authored-by: Oren Milman <orenmn@gmail.com>

Previous to commit ee171a26 the logline was working because of self.info() (now
deprecated) defaults to an empty message. 

Constructing bytes from mutating list could cause a crash.

For builtin types with builtin subclasses, help() on the type now shows up
to 4 of the subclasses. This partially replaces the exception hierarchy
information previously displayed in Python 2.7. 

If SyntaxWarning was raised as an exception, it will be replaced
with a SyntaxError for better error reporting.

Guard the `CLOCK_GETTIME` et al macros in `timemodule` based on the availability of the parent functions

Fixes doc build breakage from 890a4b92.

* bpo-34576 - Fix the formatting for security considerations in http.server.rst

* Address review comment.

This should reduce false failure reports to the Zulip 'core/test runs'
stream from Travis failures on private forks.

https://bugs.python.org/issue35032

Set SRCDIR as the current directory for git.

The symbol table was not exposing functionality to query the nonlocal symbols
in a function or to check if a particular symbol is nonlocal.

Simplify the pickling of set and dictionary objects iterators by consuming
the iterator into a list with PySequence_List.

Add restriction on the offset parameter for mmap.flush.

Explain that ALLOCATIONGRANULARITY is the same as PAGESIZE in Unix.

Initial patch by Chandan Kumar.

path_error() uses GetLastError() on Windows, but some os functions
are implemented via CRT APIs which report errors via errno.
This may result in raising OSError with invalid error code (such
as zero).

Introduce posix_path_error() function and use it where appropriate.

If buffering=1 is specified for open() in binary mode, it is silently
treated as buffering=-1 (i.e., the default buffer size).
Coupled with the fact that line buffering is always supported in Python 2,
such behavior caused several issues (e.g., bpo-10344, bpo-21332).

Warn that line buffering is not supported if open() is called with
binary mode and buffering=1.

sys and threading were imported twice.