Among the changes of turtle.py from Python 3.0 to Python 3.1 there were
three bugfixes. Those bugs appear also in the Python 2.6 version of
turtle.py

imho these should be fixed for Python 2.6.3

The appended diffs contain the (backported) fixes of these bugs,
(1) in TurtleScreen.update()
(2) in TurtleScreen.onkey()
(3) in _Screen.__init__ and _Screen.setup

The last one entails the need of adding one line into turtleDemo.py.
This change does not affect the correct working of turtleDemo with the
Python 2.6.2 turtle and demos.