pymox auto-checkout never really worked well so check-in pymox directly.

pprint.pformat is non-determinist in one test. Worked around the issue.

TEST=unit tests
BUG=none
Review URL: http://codereview.chromium.org/266043

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@29398 0039d316-1c4b-4281-b951-d872f2087c98