Backporting Idle patches from 3.x to 2.7 would be easier with a canned edit script. Below are the substitutions I can think of immediately. Do any of you know of others?

Easy (str.replace):
tkinter -> Tkinter
import tkinter.messagebox as tkMessageBox -> import tkMessageBox

A bit tricky (but still use str.replace):
OSError -> IOError
This presumes that IOError become OSError in 3.3 as well as 3.4 (#18151). But there are a few existig OSErrors is 3.3 (and that pre-existed the change in 3.4). So there would would need to be a check that a changed line matched an existing 2.7 line.

Harder (2to3 parser?):
print(arglist) -> print arglist  # but what if keyword args?
Outputting "fix print on line nn" would be easiest.

README needed (python -m) test -> (python -m) test.regrtest in the test instructions, but this should be the only place that occurs.

I might put 'edit_patch' or whatever in idle_test.