I've added 2.7 to the affected versions - the core unittest framework should be present in all 3 versions, so the choice of if/when to backport a fix and its test can be made on a case-by-case basis, rather than being a foregone conclusion due to the lack of IDLE test infrastructure in 2.7

If/when mock is used in any tests, then a compatibility module isn't actually needed, 3.3 and 3.4 can just use "from unittest import mock" while 2.7 can use "mock = support.import_module('mock')" (so those tests will run if you arrange to make the mock backport from PyPI available when running the tests, but will be skipped otherwise).

Terry, are you happy with that plan? If so, over to you to get the ball rolling and commit this as a starting point :)