Use relative import now that it is required. (Should this go into 2.5?)

Lib/test/test_sets.py

@@ -819,7 +819,8 @@ Set(['Jack', 'Jane', 'Janice', 'John', 'Marvin', 'Sam', 'Zack'])
 __test__ = {'libreftest' : libreftest}
 
 def test_main(verbose=None):
-    import test_sets, doctest
+    import doctest
+    from test import test_sets
     test_support.run_unittest(
         TestSetOfSets,
         TestExceptionPropagation,