This is the file from which the gtkpbar.py was derived.
Restructuring this reference code in order to try a new approach. It requires two threads, but this will allow the actual work function to be separated from the GUI code.
Comment; could implement vacuum as a menu option
This can't be static, or else it has to be set each time. Another signal could be added to represent that a task is already running, and thereby becoming a mutex.
Breaking out mutex idea as another class which inherits the that is not mutually exclusive.