In 3.6 importing antigravity prints a warning (although it does what it should do): >>> import antigravity /home/ivan/.../Lib/subprocess.py:761: ResourceWarning: subprocess 15501 is still running ResourceWarning, source=self) This is probably related to http://bugs.python.org/issue27069
I think this is essentially a duplicate of http://bugs.python.org/issue27069, or at least fixing that will fix this (as the exception is caused by the webbrowser.open() call)