Use string.ascii_letters instead of string.letters (SF bug #226706).
diff --git a/Lib/lib-old/codehack.py b/Lib/lib-old/codehack.py
index 52ac6be..248205b 100644
--- a/Lib/lib-old/codehack.py
+++ b/Lib/lib-old/codehack.py
@@ -31,7 +31,7 @@
# Because this is a pretty expensive hack, a cache is kept.
SET_LINENO = 127 # The opcode (see "opcode.h" in the Python source)
-identchars = string.letters + string.digits + '_' # Identifier characters
+identchars = string.ascii_letters + string.digits + '_' # Identifier characters
_namecache = {} # The cache