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.

Original patch by Josh Lynn.

Without this reset, starttls would fail if a connect/starttls was done after a
quit, because smtplib assumed the existing value of emspt_features was
accurate, but it gets reset when starttls completes (and the new value does
not contain the starttls capability, since tls is already started at that
point).  (There may be additional places where this lack of reset was an
issue as well.)

Patch by Milan Oberkirch.

Patch from Alex Gaynor.

Patch from Brian Kearns.

window is created for every test class.

Fixed Tkinter images copying operations in NoDefaultRoot mode.

Tcl command names generated for "after" callbacks now contains a name of
original function.