bpo-41521: Rename blacklist parameter to not_exported (GH-21824)

Rename "blacklist" parameter of test.support.check__all__() to
"not_exported".
diff --git a/Lib/test/test_optparse.py b/Lib/test/test_optparse.py
index ed65b77..1ed6bf9 100644
--- a/Lib/test/test_optparse.py
+++ b/Lib/test/test_optparse.py
@@ -1652,8 +1652,8 @@
 
 class MiscTestCase(unittest.TestCase):
     def test__all__(self):
-        blacklist = {'check_builtin', 'AmbiguousOptionError', 'NO_DEFAULT'}
-        support.check__all__(self, optparse, blacklist=blacklist)
+        not_exported = {'check_builtin', 'AmbiguousOptionError', 'NO_DEFAULT'}
+        support.check__all__(self, optparse, not_exported=not_exported)
 
 
 def test_main():