Ubuntu 12.04 64-bit
Python 2.7.3 (virtualenv)
Hi, just adding a few info, hope not completely useless, that seem related to the issue. I got the same message when running nosetests against my source. It's an application using Tkinter as frontend. All tests pass, though. Besides, I always destroy root in tearDown().
I noticed that the the issue only comes up when i run tests without specifying any path, like in nosetests -vs.
If i enter nosetests -vs tests/unit/ tests/integration/ everything runs smooth.