sympy/sympy — pull request #1464 by scolobb (2012-08-04 12:12:15+00:00)
Title: Set: Fix the sort_key.

Unfortunately, I haven't been sufficiently diligent to thoroughly check the recent `sort_key`-related modification, so two slight issues with `Set.sort_key` have slipped into `master`, sorry.

I hope the changes here are pretty straightforward and we will be able to merge them soon.