Index: django/utils/html.py
===================================================================
--- django/utils/html.py        (revision 6442)
+++ django/utils/html.py        (working copy)
@@ -80,7 +80,7 @@
         if match:
             lead, middle, trail = match.groups()
             if middle.startswith('www.') or ('@' not in middle and not middle.startswith('http://') and \
-                    len(middle) > 0 and middle[0] in string.letters + string.digits and \
+                    len(middle) > 0 and middle[0] in string.ascii_letters + string.digits and \
                     (middle.endswith('.org') or middle.endswith('.net') or middle.endswith('.com'))):
                 middle = '<a href="http://%s"%s>%s</a>' % (middle, nofollow_attr, trim_url(middle))
             if middle.startswith('http://') or middle.startswith('https://'):