use assert[Not]In where appropriate
diff --git a/Lib/test/test_errno.py b/Lib/test/test_errno.py
index 4adc1f0..bb8918f 100755
--- a/Lib/test/test_errno.py
+++ b/Lib/test/test_errno.py
@@ -28,8 +28,8 @@
     def test_attributes_in_errorcode(self):
         for attribute in errno.__dict__.iterkeys():
             if attribute.isupper():
-                self.assertTrue(getattr(errno, attribute) in errno.errorcode,
-                             'no %s attr in errno.errorcode' % attribute)
+                self.assertIn(getattr(errno, attribute), errno.errorcode,
+                              'no %s attr in errno.errorcode' % attribute)
 
 
 def test_main():