Make test_str.py pass.
diff --git a/Lib/encodings/base64_codec.py b/Lib/encodings/base64_codec.py
index f84e780..e6a1e65 100644
--- a/Lib/encodings/base64_codec.py
+++ b/Lib/encodings/base64_codec.py
@@ -21,7 +21,7 @@
 
     """
     assert errors == 'strict'
-    output = base64.encodestring(input)
+    output = bytes(base64.encodestring(input))
     return (output, len(input))
 
 def base64_decode(input,errors='strict'):