Make parrot-b2 benchmark python 3.7 compatible

Author: msimacek

graalpython/benchmarks/src/meso/parrot-b2.py

@@ -1,7 +1,7 @@
 #!/usr/bin/env python
 # Copyright 2008-2010 Isaac Gouy
 # Copyright (c) 2013, 2014, Regents of the University of California
-# Copyright (c) 2017, 2018, Oracle and/or its affiliates.
+# Copyright (c) 2017, 2020, Oracle and/or its affiliates.
 # All rights reserved.
 #
 # Revised BSD license
@@ -91,7 +91,10 @@ def main(num):
 def _zip(a, b):
     iter_a = iter(a)
     for elem in b:
-        yield next(iter_a), elem
+        try:
+            yield next(iter_a), elem
+        except StopIteration:
+            return
 
 
 def measure(num):