Run unit tests from executable Python modules
When developing on a Linux VM inside a Windows host, all Python modules have the executable flag on. Nose has work around for this when run on Windows (https://github.com/nose-devs/nose/blob/master/nose/config.py#L26). In this case, the Python intrepeter run inside the VM causing the work-around to fail. This review request adds check for executable file permission and forces Nose to run tests.

Unit tests pass.