Fallback to unittest2 when necessary

NEWS.rst

@@ -4,7 +4,7 @@ Release History
 0.4.0 (2012-05-??)
 ~~~~~~~~~~~~~~~~~~
 
-* TBD
+* Fall back to unittest2 if unittest is missing required functionality
 
 
 0.3.1 (2012-01-17)

setup.py

@@ -1,6 +1,9 @@
 #!/usr/bin/env python
 from distutils.core import setup
 
+# Technically, unittest2 is a dependency to run the tests on 2.6 and 3.1
+# Not sure how best to express that cleanly here
+
 setup(
     name='contextlib2',
     version=open('VERSION.txt').read().strip(),

test_contextlib2.py

@@ -1,8 +1,11 @@
 #!/usr/bin/env python
-"""Unit tests for contextlib.py, and other context managers."""
+"""Unit tests for contextlib2"""
 
 import sys
+
 import unittest
+if not hasattr(unittest, "skipIf"):
+    import unittest2 as unittest
 
 from contextlib2 import *  # Tests __all__