Handle more file open/close with "with"

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

In Python 3, the default string type is now the Python 2 unicode
strings.  The unicode strings cannot be converted to a byte stream,
so we have to convert it before writing to the streams.

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.