Kivy app confirm exit

from kivy.config import Config
Config.set('kivy', 'exit_on_escape', '0')

from kivy.app import App
from kivy.uix.label import Label
from kivy.uix.boxlayout import BoxLayout
from kivy.uix.button import Button
from kivy.uix.popup import Popup
from kivy.core.window import Window


class ChildApp(App):

    def build(self):
        Window.bind(on_request_close=self.on_request_close)
        return Label(text='Child')

    def on_request_close(self, *args):
        self.textpopup(title='Exit', text='Are you sure?')
        return True

    def textpopup(self, title='', text=''):
        """Open the pop-up with the name.

        :param title: title of the pop-up to open
        :type title: str
        :param text: main text of the pop-up to open
        :type text: str
        :rtype: None
        """
        box = BoxLayout(orientation='vertical')
        box.add_widget(Label(text=text))
        mybutton = Button(text='OK', size_hint=(1, 0.25))
        box.add_widget(mybutton)
        popup = Popup(title=title, content=box, size_hint=(None, None), size=(600, 300))
        mybutton.bind(on_release=self.stop)
        popup.open()


if __name__ == '__main__':
    ChildApp().run()