Issue #23671: string.Template now allows to specify the "self" parameter as
keyword argument.  string.Formatter now allows to specify the "self" and
the "format_string" parameters as keyword arguments.
diff --git a/Lib/test/test_string.py b/Lib/test/test_string.py
index e786ab6..fdb3253 100644
--- a/Lib/test/test_string.py
+++ b/Lib/test/test_string.py
@@ -196,6 +196,18 @@
         self.assertRaises(ValueError, format, '', '#')
         self.assertRaises(ValueError, format, '', '#20')
 
+    def test_format_keyword_arguments(self):
+        fmt = string.Formatter()
+        self.assertEqual(fmt.format("-{arg}-", arg='test'), '-test-')
+        self.assertRaises(KeyError, fmt.format, "-{arg}-")
+        self.assertEqual(fmt.format("-{self}-", self='test'), '-test-')
+        self.assertRaises(KeyError, fmt.format, "-{self}-")
+        self.assertEqual(fmt.format("-{format_string}-", format_string='test'),
+                         '-test-')
+        self.assertRaises(KeyError, fmt.format, "-{format_string}-")
+        self.assertEqual(fmt.format(arg='test', format_string="-{arg}-"),
+                         '-test-')
+
 class BytesAliasTest(unittest.TestCase):
 
     def test_builtin(self):