def _preview(self):
        """ Preview the .ui file.  Return the exit status to be passed back to
        the parent process.
        """

        from PyQt5 import QtWidgets

        app = QtWidgets.QApplication([self._ui_file])
        widget = loadUi(self._ui_file)
        widget.show()

        return app.exec_()
Preview the .ui file.  Return the exit status to be passed back to
        the parent process.