Make this bytes thing actually work :/

The wrong `b` was defined for Python 2.6 and Python 2.7.  Shocking this did not cause problems earlier.
diff --git a/OpenSSL/test/util.py b/OpenSSL/test/util.py
index e5b5dc3..59d6a60 100644
--- a/OpenSSL/test/util.py
+++ b/OpenSSL/test/util.py
@@ -15,16 +15,14 @@
 
 from OpenSSL.crypto import Error, _exception_from_error_queue
 
-
-try:
-    bytes = bytes
-except NameError:
+if sys.version_info < (3, 0):
     def b(s):
         return s
     bytes = str
 else:
     def b(s):
         return s.encode("ascii")
+    bytes = bytes
 
 
 class TestCase(TestCase):