Fix another Python 3 issue.
Remove odd (but necessary before we dropped Python 2.6 support) use of the external argparse package.
Exclude six from listings.
Don't hide the output of pip-sync.

This caused some confusion as to whether or not this should work.  As of
yet, the pip-sync tool is unimplemented and so this test is not expected
to pass at all.  It was recorded as a "contract" on how pip-sync should
work.
Remove support for pip-review on future branch completely.

It has been obsoleted by the pip list --outdated command anyway.