Correct a couple of errors in the updated catch_warning documentation (the Py3k version was fixed before being checked in)
diff --git a/Doc/library/test.rst b/Doc/library/test.rst
index 46d21cc..4c95759 100644
--- a/Doc/library/test.rst
+++ b/Doc/library/test.rst
@@ -305,9 +305,9 @@
       with catch_warning() as w:
           warnings.simplefilter("always")
           warnings.warn("foo")
-          assert w.last == "foo"
+          assert str(w.message) == "foo"
           warnings.warn("bar")
-          assert w.last == "bar"
+          assert str(w.message) == "bar"
           assert str(w.warnings[0].message) == "foo"
           assert str(w.warnings[1].message) == "bar"