[3.9] bpo-37116: Use PEP 570 syntax for positional-only parameters. (GH-12620)

Turn deprecation warnings added in 3.8 into TypeError.
diff --git a/Lib/test/test_userdict.py b/Lib/test/test_userdict.py
index 662c7f6..483910a 100644
--- a/Lib/test/test_userdict.py
+++ b/Lib/test/test_userdict.py
@@ -30,8 +30,8 @@
         self.assertEqual(collections.UserDict(one=1, two=2), d2)
         # item sequence constructor
         self.assertEqual(collections.UserDict([('one',1), ('two',2)]), d2)
-        with self.assertWarnsRegex(DeprecationWarning, "'dict'"):
-            self.assertEqual(collections.UserDict(dict=[('one',1), ('two',2)]), d2)
+        self.assertEqual(collections.UserDict(dict=[('one',1), ('two',2)]),
+                         {'dict': [('one', 1), ('two', 2)]})
         # both together
         self.assertEqual(collections.UserDict([('one',1), ('two',2)], two=3, three=5), d3)
 
@@ -149,9 +149,8 @@
                          [('dict', 42)])
         self.assertEqual(list(collections.UserDict({}, dict=None).items()),
                          [('dict', None)])
-        with self.assertWarnsRegex(DeprecationWarning, "'dict'"):
-            self.assertEqual(list(collections.UserDict(dict={'a': 42}).items()),
-                             [('a', 42)])
+        self.assertEqual(list(collections.UserDict(dict={'a': 42}).items()),
+                         [('dict', {'a': 42})])
         self.assertRaises(TypeError, collections.UserDict, 42)
         self.assertRaises(TypeError, collections.UserDict, (), ())
         self.assertRaises(TypeError, collections.UserDict.__init__)