diff -r b6ebc726d5fe Lib/email/quoprimime.py
--- a/Lib/email/quoprimime.py	Sat Jul 06 13:25:44 2013 +0200
+++ b/Lib/email/quoprimime.py	Sat Jul 06 16:20:34 2013 +0400
@@ -319,4 +319,4 @@
     the high level email.header class for that functionality.
     """
     s = s.replace('_', ' ')
-    return re.sub(r'=[a-fA-F0-9]{2}', _unquote_match, s, re.ASCII)
+    return re.sub(r'=[a-fA-F0-9]{2}', _unquote_match, s, flags=re.ASCII)