Demote warnings to notices where appropriate, following the goal that as few "red box" warnings
should clutter the docs as possible.  Part 1: stuff that gets merged to Py3k.
diff --git a/Doc/library/unittest.rst b/Doc/library/unittest.rst
index 50314cd..6b19c29 100644
--- a/Doc/library/unittest.rst
+++ b/Doc/library/unittest.rst
@@ -1086,7 +1086,7 @@
       creates an instance of the class for each test method defined for the
       class.
 
-      .. warning::
+      .. note::
 
          While using a hierarchy of :class:`TestCase`\ -derived classes can be
          convenient in sharing fixtures and helper functions, defining test