tests: Add missing backwards compat methods for Python 2.6
tests: Add missing backwards compat methods for Python 2.6

Define skipIf(), assertLess(), and assertLessEqual() for running the tests with
Python 2.6.

https://bugzilla.gnome.org/show_bug.cgi?id=691646

davibe/pygobject,GNOME/pygobject,davibe/pygobject,sfeltman/pygobject,pexip/pygobject,davibe/pygobject,sfeltman/pygobject,GNOME/pygobject,davibe/pygobject,sfeltman/pygobject,GNOME/pygobject,pexip/pygobject,pexip/pygobject