Exception when setting exit_on_escape

[matham]

If you run the following code:

from kivy.config import Config
Config.set('kivy', 'exit_on_escape', 0)
from kivy.base import EventLoop
EventLoop.ensure_window()
Config.set('kivy', 'exit_on_escape', 1)

You'll get the following exception:

     Config.set('kivy', 'exit_on_escape', 1)
   File "C:\kivy-dev\kivy\kivy\config.py", line 313, in set
     self._do_callbacks(section, option, value)
   File "C:\kivy-dev\kivy\kivy\config.py", line 278, in _do_callbacks
     callback(section, key, value)
   File "C:\kivy-dev\kivy\kivy\core\window\__init__.py", line 801, in __exit
     WindowBase.on_keyboard.exit_on_escape = value
 AttributeError: 'instancemethod' object has no attribute 'exit_on_escape'

This post seems to describe why this is happening: https://stackoverflow.com/questions/7034063/adding-attributes-to-instancemethods-in-python. From there the fix seems to be to change WindowBase.on_keyboard.exit_on_escape = value to WindowBase.on_keyboard.__func__.exit_on_escape = value. However, they also seem to imply that it is different between python 2 and 3, so I'm not sure that is the proper fix.

[mihaineacsu]

@matham How about using WindowBase.__dict__['on_keyboard'].exit_on_escape = value ?
This would work on both Python 2 and 3.

[matham]

@mihaineacsu Submit a pr for it :)

[mihaineacsu]

Fixed via #1970 . Can be closed.