AttributeError when sys.stderr is None.

For 2,.7, add print_function __future__ import and convert print statements
to print functions.  Based on 3.x patch by Serhiy Storchaka.

focussed and move advanced section and customization information to a separate
file called appendix.

Patch credits: Jamayla Wiley, Ya-Ting Huang and James Brewer.

combined with non-standard cookie handling in some Web browsers.

Reported by Sergey Bobrov.

when it is run with pythonw.exe.

Documented that Tk.report_callback_exception() is purposed to be overriden in
applications.

Simplified existing detections of Unicode-disabled build.

Fix build_tkinter.py.
Update msi.py to use environment vars and correct tcl/tk paths.
Update msilib.py to generate short names for files with multiple dots in the name.

Fix the warning: "test_support.TESTFN was modified by test_distutils".

character instead of truncate it.  Based on patch by Victor Stinner.

empty string or tuple argument.

On some platforms Tcl memory allocator returns NULL when allocating zero-sized
block of memory.

ckalloc() causes the Tcl interpreter to panic, attemptckalloc() returns NULL
if the memory allocation fails.

  Update zlib file names for the PC installers

First letter no longer is stripped from the "status" key in
the result of Treeview.heading().

a pipe in _ipconfig_getnode().

because the Doc Makefile has been changed to no longer download sphinx
and its dependencies, build-installer.py now requires that there be an
externally-supplied sphinx-build available.

as of 2.7.9, doc builds require an externally installed sphinx-build
like 3.4+ builds do.

next() function).

The progress bar helps a lot to analyze noisy buildbot logs, to find quickly
where errors occurred.

* Now the source encoding declaration on the second line isn't effective if
  the first line contains anything except a comment.  This affects compile(),
  eval() and exec() too.

* IDLE now ignores the source encoding declaration on the second line if the
  first line contains anything except a comment.

* 2to3 and the findnocoding.py script now ignore the source encoding
  declaration on the second line if the first line contains anything except
  a comment.

Users are now required to install Sphinx themselves as is already the case with
the Python 3 branch.

Backport from default.