Create a zip backup with a GUI progress bar.

def _backup_pb_gui(self, dirs):
        """Create a zip backup with a GUI progress bar."""
        import PySimpleGUI as sg
        # Legacy support
        with ZipFile(self.zip_filename, 'w') as backup_zip:
            for count, path in enumerate(dirs):
                backup_zip.write(path, path[len(self.source):len(path)])
                if not sg.OneLineProgressMeter('Writing Zip Files', count + 1, len(dirs) - 1, 'Files'):
                    break