def on_cleanup_error(function, path, excinfo):
                click.secho("warning: failed to remove file or directory: {}\n"
                            "please delete it manually.".format(path),
                            fg="red")
def on_lower_bound_changed(self):
        self.ui.spinBoxUpperBound.setMinimum(self.ui.spinBoxLowerBound.value())
        self.ui.spinBoxBoundaryNumber.setMaximum(math.ceil((self.ui.spinBoxUpperBound.value()
                                                            - self.ui.spinBoxLowerBound.value()) / 2))