Issue 1781. Now ConfigParser.add_section does not let you add a
DEFAULT section any more, because it duplicated sections with
the rest of the machinery. Thanks Tim Lesher and Manuel Kaufmann.
diff --git a/Lib/test/test_cfgparser.py b/Lib/test/test_cfgparser.py
index c4df741..a8b5d7c 100644
--- a/Lib/test/test_cfgparser.py
+++ b/Lib/test/test_cfgparser.py
@@ -446,6 +446,14 @@
         self.assertRaises(TypeError, cf.set, "sect", "option2", 1.0)
         self.assertRaises(TypeError, cf.set, "sect", "option2", object())
 
+    def test_add_section_default_1(self):
+        cf = self.newconfig()
+        self.assertRaises(ValueError, cf.add_section, "default")
+
+    def test_add_section_default_2(self):
+        cf = self.newconfig()
+        self.assertRaises(ValueError, cf.add_section, "DEFAULT")
+
 class SortedTestCase(RawConfigParserTestCase):
     def newconfig(self, defaults=None):
         self.cf = self.config_class(defaults=defaults, dict_type=SortedDict)