[bugfix] Terminate QuitKeyboardInterrupt sucessfully
[bugfix] Terminate QuitKeyboardInterrupt sucessfully

Terminate a BaseBot script sucessfully even when an input answer is [q]uit
which raises QuitKeyboardInterrupt. On Python 2 Plattforms this terminates
as an exception.

Bug: T195687
Change-Id: I284e2452521fe5915d7e9d6451ee2729869cf16e

wikimedia/pywikibot-core,PersianWikipedia/pywikibot-core,wikimedia/pywikibot-core