Use Python 2.7 unittest syntax in our unittests
https://bugs.webkit.org/show_bug.cgi?id=105607

Patch by Tim 'mithro' Ansell <mithro@mithis.com> on 2013-01-22
Reviewed by Eric Seidel.

* Scripts/webkitpy/**/*_unittest.py:

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@140510 268f45cc-cd09-0410-ab3c-d52691b4dbfc