sympy/sympy — pull request #1211 by agmps18 (2012-04-05 19:40:15+00:00)
Title: 2210:Sum doesn't set commutativity

earlier:
>>>Sum(1, (x, 1, 1)).is_commutative
none

now
>>>Sum(1, (x, 1, 1)).is_commutative
True
Sum(x*y, (x, 1, 2), (y, 1, 3)).is_commutative
True