In my environment, with:

- LANGUAGE=en_US:en_GB:en:C
- LC_ALL=en_US.UTF-8

Running the testsuite with:

- python3.6 -m pytest: is successful
- tox -e py36: fails

The later because LC_ALL is unset by tox, and LANGUAGE is not passed
through, so `locale.getpreferredencoding()` returns 'ANSI_X3.4-1968'.

So it's possible to run tox with something like:
`py.test -k test_unicode_filename_in_sdist`, and
not loose the default report arguments.

Restrict use of os.makedirs to those with the security patch introduced in Python 3.2.6, 3.3.5, and 3.4.1 per https://bugs.python.org/issue21082. Ref #1082.

fixed #1042 -- updates an import to use six from the vendored package

Document -s to run single test

Fixes https://github.com/pypa/setuptools/issues/1032

Tox doc comments

This will help get new contributors started, if they're just used to
running "tox".