Issue #13913: normalize utf-8 codec name in UTF-8 decoder
diff --git a/Objects/unicodeobject.c b/Objects/unicodeobject.c
index f51d4d0..70856f5 100644
--- a/Objects/unicodeobject.c
+++ b/Objects/unicodeobject.c
@@ -2763,7 +2763,7 @@
         outpos = p-PyUnicode_AS_UNICODE(unicode);
         if (unicode_decode_call_errorhandler(
                 errors, &errorHandler,
-                "utf8", errmsg,
+                "utf-8", errmsg,
                 &starts, &e, &startinpos, &endinpos, &exc, &s,
                 &unicode, &outpos, &p))
             goto onError;