Remove string.{letters,lowercase,uppercase}.
diff --git a/Tools/scripts/texi2html.py b/Tools/scripts/texi2html.py
index e5e292d..37d6e91 100755
--- a/Tools/scripts/texi2html.py
+++ b/Tools/scripts/texi2html.py
@@ -2000,7 +2000,7 @@
 def increment(s):
     if not s:
         return '1'
-    for sequence in string.digits, string.lowercase, string.uppercase:
+    for sequence in string.digits, string.ascii_lowercase, string.ascii_uppercase:
         lastc = s[-1]
         if lastc in sequence:
             i = sequence.index(lastc) + 1