It looks like their website changed.
Traceback (most recent call last):
File "comcastBandwidth.py", line 233, in <module>
usage = comcast.currentUsage()
File "comcastBandwidth.py", line 78, in currentUsage
sign_link = br.find_link(text="Sign In")
File "/home/eswanson/build/comcast-bw/venv/lib/python2.7/site-packages/mechanize/_mechanize.py", line 620, in find_link
raise LinkNotFoundError()
mechanize._mechanize.LinkNotFoundError
It looks like their website changed.