Thanks for the tip, indeed the debug console throws me some interesting output:

PYDEV DEBUGGER WARNING:
sys.settrace() should not be used when the debugger is being used.
This may cause the debugger to stop working correctly.
If this is needed, please check: 
http://pydev.blogspot.com/2007/06/why-cant-pydev-debugger-work-with.html
to see how to restore the debug tracing back correctly.
Call Location:
  File "c:\Users\my_project_directory\env\lib\site-packages\coverage\collector.py", line 292, in _installation_trace
    sys.settrace(None)

I'm in the works of googling this... A bit confused, though, why this problem shows up.