Fix testcodec.py and test_charmapcodec.py
diff --git a/Lib/test/testcodec.py b/Lib/test/testcodec.py
index 7ac9203..e7f836b 100644
--- a/Lib/test/testcodec.py
+++ b/Lib/test/testcodec.py
@@ -36,7 +36,7 @@
 decoding_map = codecs.make_identity_dict(range(256))
 decoding_map.update({
         0x78: "abc", # 1-n decoding mapping
-        "abc": 0x0078,# 1-n encoding mapping
+        str8("abc"): 0x0078,# 1-n encoding mapping
         0x01: None,   # decoding mapping to <undefined>
         0x79: "",    # decoding mapping to <remove character>
 })