Python is not a strongly typed language and renaming variables in such a language is a minefield. I've used PyCharm and WebStorm and never felt comfortable using their variable rename facilities for Python and Javascript. If they do it better than rope then that's good, but you need to write those languages in a very specific if you want IDE renamings to succeed. IMO, that rope fails silently might be viewed as more of a feature than a bug :). Anyway, I'm sure it will be improved.
