Fix trivial bug in idna encoding.
diff --git a/Lib/encodings/idna.py b/Lib/encodings/idna.py
index d9322a1..b226d22 100644
--- a/Lib/encodings/idna.py
+++ b/Lib/encodings/idna.py
@@ -8,7 +8,6 @@
 
 # IDNA section 5
 ace_prefix = "xn--"
-uace_prefix = str(ace_prefix, "ascii")
 
 # This assumes query strings, so AllowUnassigned is true
 def nameprep(label):