django.conf.urls.defaults has been removed in Django 1.6. If the problem was in your own code, you would fix it by changing the import to
from django.conf.urls import patterns, url, include
However, in your case the problem is in a third party app, graphite. The issue has been fixed in graphite’s master branch and version 0.9.14+.
In Django 1.8+ you can remove patterns from the import, and use a list of url()s instead.
from django.conf.urls import url, include