django/django — pull request #2937 by rprince (2014-07-21 22:37:58+00:00)
Title: Warning to reader that the regex capture group name has changed

The snippet doesn't make it obvious that the capture group has changed (it was poll_id earlier in the tutorial), and it's easy to be distracted by the other changes in the line and miss this.

It's common enough that there's even a StackOverflow question about it:
http://stackoverflow.com/questions/12304050/django-tutorial-generic-views-attribute-error