We're using nose to run our tests. Easy test discovery and so. So I also went after some existing internal libraries and simplified the test running there.
There were problems though with one library: the docstrings inside the python modules weren't being run. In a similar setup in another library, everything was fine.
I googled some and found the answer on stackoverflow: nose by default skips executable *.py files...
And the files in that single library were executable for historical reasons...
Solution: pass the --exe option to nose and they're not skipped anymore.