I am seeing this error (which means I cannot run tests) in the Python plugin in Intellij U - both the 10.5 release (107.105) and the latest EAP (107.148).
The test case that I am trying to run is http://code.google.com/p/lepl/source/browse/src/lepl/_example/expression.py - note that it is a subclass of a subclass of TestCase.
If I try a more normal situation (subclasses of TestCase) then I see "No tests were found" - http://code.google.com/p/lepl/source/browse/src/lepl/matchers/combine.py for example
In both cases the Python plugin is 2.7.0 and I am using Python 3.2 in a virtualenv (but I see the same if I use /usr/local/bin/python3.2).
Previously reported at http://devnet.jetbrains.net/thread/304707?tstart=0