nicira_role: add module description
diff --git a/tests/nicira_role.py b/tests/nicira_role.py
index 584188b..a10d8b8 100644
--- a/tests/nicira_role.py
+++ b/tests/nicira_role.py
@@ -1,4 +1,5 @@
 """
+Test the Nicira controller role extension
 """
 import struct
 import unittest