test_unloading_community breaks because nosetest uses BufferingHandler.

nosetests uses BufferingHandler to capture output.  This handler keeps
references to the community, breaking this test.

This test must be run separately with logcapture disabled.  Note that
this results in no output.

nosetests --no-skip --nologcapture tests/test_classification.py:TestClassification.test_unloading_community