Python 3 fix for PR: #172 from dato-code/added-groupby-aggregates

PR #172 fails on Python 3 because of None comparisons.
- In Python 2: None < 1
- In Python 3: None < 2 returns an error.

The test case was changed to compare list([1,None]) where the order is
interchangable to comparisons on set([1,None]).

Author: srikris

oss_src/unity/python/sframe/test/test_sframe.py

@@ -1151,8 +1151,8 @@ def test_min_max_with_missing_values(self):
         self.assertEqual(sf2['Var of value'], [1, 0])
         self.assertEqual(sf2['Stdv of value'], [1, 0])
         self.assertEqual(sf2['Count Distinct of value'], [2, 1])
-        self.assertEqual(sorted(sf2['Distinct of value'][0]), sorted([1, None]))
-        self.assertEqual(sorted(sf2['Distinct of value'][1]), sorted([None]))
+        self.assertEqual(set(sf2['Distinct of value'][0]), set([1, None]))
+        self.assertEqual(set(sf2['Distinct of value'][1]), set([None]))
         self.assertEqual(sf2['Frequency Count of value'][0], {1:1, None:5})
         self.assertEqual(sf2['Frequency Count of value'][1], {None:4})