+
+ Driver can connect to app on errors in `on.quit` (and `on.save_settings`).
+ * clone this repo to a new client app, clear its save dir, run it, run the
+ driver, define `on.quit` with a run-time error:
+ ```
+ on.quit = function()
+ foo = bar+1
+ end
+ ```
+ Hit F4.
+ Try to quit the client app. It shows an error and refuses to quit.
+ Edit `on.quit` in the driver and remove the error:
+ ```
+ on.quit = function()
+ end
+ ```
+ Hit F4. The error disappears from the app and driver.
+ Try to quit the client app. Now the quit succeeds.
+
+ * clone this repo to a new client app, clear its save dir, run it, run the
+ driver, define `on.quit` with a run-time error:
+ ```
+ on.quit = function()
+ foo = bar+1
+ end
+ ```
+ Hit F4.
+ Try to quit the client app. It shows an error and refuses to quit.
+ Hit F4 again in the driver (without fixing the error).
+ Try to quit the client app again. It continues to show the error.