--- a/tests/test-ancestor.py	Sun May 28 00:12:38 2017 +0200
+++ b/tests/test-ancestor.py	Sat Jun 17 14:38:02 2017 +0530
@@ -42,7 +42,7 @@
                 p1 = i - 1
             else:
                 p1 = rng.randrange(i - 1)
-            p2 = rng.choice(range(0, p1) + range(p1 + 1, i))
+            p2 = rng.choice(list(range(0, p1)) + list(range(p1 + 1, i)))
             graph[i] = [p1, p2]
         elif rng.random() < prevprob:
             graph[i] = [i - 1]