Normalize the encoding names for Latin-1 and UTF-8 to
'latin-1' and 'utf-8'.

These are optimized in the Python Unicode implementation
to result in more direct processing, bypassing the codec
registry.

Also see issue11303.
diff --git a/Lib/test/test_strlit.py b/Lib/test/test_strlit.py
index 23d96f8..2bcf4d1 100644
--- a/Lib/test/test_strlit.py
+++ b/Lib/test/test_strlit.py
@@ -130,7 +130,7 @@
         self.assertRaises(SyntaxError, self.check_encoding, "utf-8", extra)
 
     def test_file_utf8(self):
-        self.check_encoding("utf8")
+        self.check_encoding("utf-8")
 
     def test_file_iso_8859_1(self):
         self.check_encoding("iso-8859-1")