unknown-horizons/unknown-horizons — pull request #32 by volpino (2012-03-17 12:20:59+00:00)
Title: Update horizons/session.py

The problem is here
```
self.selection_groups = [set()] * 10
```

set() is mutable so i think it's a bug.
The list contains 10 references to the same object

```
>>> a = [set()] * 10
>>> a[0].add(5)
>>> a
[set([5]), set([5]), set([5]), set([5]), set([5]), set([5]), set([5]), set([5]), set([5]), set([5])]
```