Exceptions
Exceptions that might make sense to be used outside the library.
Cancelled
User has cancelled. A SystemExit based exception noting that the program exits without a traceback, ex. if user hits the escape or closes the window.
ValidationFail
Signal to the form that submit failed and we want to restore it.
InterfaceNotAvailable
Interface failed to init, ex. display not available in GUI. Or the underlying dependency was uninstalled.