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_sax.py b/Lib/test/test_sax.py
index 0f6a1ca..bddb375 100644
--- a/Lib/test/test_sax.py
+++ b/Lib/test/test_sax.py
@@ -20,8 +20,8 @@
 TEST_XMLFILE = findfile("test.xml", subdir="xmltestdata")
 TEST_XMLFILE_OUT = findfile("test.xml.out", subdir="xmltestdata")
 try:
-    TEST_XMLFILE.encode("utf8")
-    TEST_XMLFILE_OUT.encode("utf8")
+    TEST_XMLFILE.encode("utf-8")
+    TEST_XMLFILE_OUT.encode("utf-8")
 except UnicodeEncodeError:
     raise unittest.SkipTest("filename is not encodable to utf8")