Add missing import 'types'

The commit 6950c04614d0bd1fc9c61b79ec7e2be0d16abdc4 did the following,
but missed to import the 'types' module:

-    module = imp.new_module(name)
+    module = types.ModuleType(name)

tests/modules/lib/__init__.py

@@ -1,6 +1,7 @@
 # vim:fileencoding=utf-8:noet
 from __future__ import (unicode_literals, division, absolute_import, print_function)
 
+import types
 import sys