SF bug #1460340:  random.sample can raise KeyError

Fix the hit and miss style of testing for sets and dicts.
diff --git a/Lib/test/test_random.py b/Lib/test/test_random.py
index 9c2e0d0..c9431b3 100644
--- a/Lib/test/test_random.py
+++ b/Lib/test/test_random.py
@@ -96,6 +96,9 @@
         self.gen.sample(dict.fromkeys('abcdefghijklmnopqrst'), 2)
         self.gen.sample(str('abcdefghijklmnopqrst'), 2)
         self.gen.sample(tuple('abcdefghijklmnopqrst'), 2)
+        # SF bug #1460340 -- random.sample can raise KeyError
+        a = dict.fromkeys(range(10)+range(10,100,2)+range(100,110))
+        self.gen.sample(a,3)
 
     def test_gauss(self):
         # Ensure that the seed() method initializes all the hidden state.  In