Subprocess32

-----------------
* Promoted 3.5.4rc2 to become 3.5.4.

-----------------

-----------------
* GitHub [57]: TimeoutExpired and CalledProcessError exceptions can now
be unpickled.

-----------------

-----------------
* GitHub [61]: Backport the fixes for https://bugs.python.org/issue10963,
https://bugs.python.org/issue19612, and https://bugs.python.org/issue30418.
When a child process was so short lived it dies or closes its pipes before
you call communicate(). When supplying stdin or reading its output in
this scenario, do not raise an unexpected broken pipe or interrupted
system call exception.

-----------------

-----------------
* Disallow ridiculously large numbers (millions) of arguments. [54]

-----------------

-----------------
* Explicitly include <signal.h> in _posixsubprocess_helpers.c; it already
gets configure checked and pulled in via Python's own <Python.h> in many
circumstances but it is better to be explicit. IWYU
If you were using subprocess32 on a Python interpreter built *without*
the --with-fpectl configure option enabled, restore_signals is now
useful rather than a no-op. I do not know if such builds were common.
* Adds a functional test for restore_signals=True behavior.

-----------------

-----------------
* Fix AttributeError: 'module' object has no attribute 'Signals' when
constructing a CalledProcessError exception. [49]

-----------------