+ On Windows, you cannot write onto a file held by another live
file-pointer (test_pack.py:#L204).
+ The TC fails later, on clean up (the usual).

Handle more file open/close with "with"

autopep8 -v -j 8 --max-line-length 120 --in-place --recursive

range in py2 will return a list, which can mean a lot of time and memory
is spent on generating it even though it's just used for iteration.

Simplified implementation of MAXSIZE

This fixes most of the import errors that came from using the
implicit relative imports that Python 2 supports.  This also fixes
the use of `xrange`, which has replaced `range` in Python 3.  The
same has happened for `izip`, which is also being aliased.

The octal number syntax changed in Python 3, so we are now
converting from strings using the `int` built-in function, which
will produce the same output across both versions of Python.