BUG: leftover kernel processes

[nwhitehead]

Sometimes when you do lots of interrupting and restarting, or if you encounter errors in the app, you can quit the app and end up with python processes still running waiting forever. They should be cleaned up without fail, even in weird cases.

[mangecoeur]

I ran into this working on ipython-desktop. I dealt with it by recording all the process PIDs created by ipython - ipython used to create a file in the .ipython folder for each kernal, not sure if this is still the case - and forcing the system to kill the process by PID before shutdown.