Index: Lib/encodings/__init__.py
===================================================================
--- Lib/encodings/__init__.py	(revision 55807)
+++ Lib/encodings/__init__.py	(working copy)
@@ -60,11 +60,8 @@
     """
     # Make sure we have an 8-bit string, because .translate() works
     # differently for Unicode strings.
-    if isinstance(encoding, str):
-        # Note that .encode('latin-1') does *not* use the codec
-        # registry, so this call doesn't recurse. (See unicodeobject.c
-        # PyUnicode_AsEncodedString() for details)
-        encoding = encoding.encode('latin-1')
+    if not isinstance(encoding, str8):
+        encoding = str8(encoding)
     return '_'.join(encoding.translate(_norm_encoding_map).split())
 
 def search_function(encoding):