Catch runtime error in iterator tests

Summary: This is causing errors to be displayed in the test output.

Reviewed By: alexmalyshev

Differential Revision: D67205100

fbshipit-source-id: 2764562e16d0b124a826e2f80f5a2305e2434595

test_concurrent.py

@@ -766,7 +766,13 @@ def test_iterator_failure(self):
         iterator._dict = BreakingDict()
 
         def worker():
-            iterator.insert(0, None)
+            try:
+                iterator.insert(0, None)
+            except RuntimeError:
+                # We want the insert to fail and set the internal flag to
+                # indicate that a failure occurred. We don't want the error to
+                # propagate further than this.
+                pass
 
         t = threading.Thread(target=worker)
         t.start()