In the section "Increase Test Coverage" of the DevGuide : https://docs.python.org/devguide/_sources/coverage.txt

You can read this paragraph where there is a url for a website, but the website is out-of-date and don't reflect the right version of Python.

"""
Choosing what module you want to increase test coverage for can be done in a
couple of ways.
A third-party website at http://coverage.livinglogic.de/ provides an
overall view of how good coverage is for various modules (you will want to
focus on those in the ``Lib`` directory as those are the pure Python modules
from Python's stdlib, and thus easier to work with than the C extension
modules). But since this is a third-party site we cannot promise that it will
always be accessible or have useful information (i.e., be working properly).
"""


"""
Python code coverage
Generated at 2013-08-14 08:28:40

Last commit at 2013-08-14 03:34:49 by Raymond Hettinger

Changeset identification hash ac2f59a6637f0cc69c4a5541195ce752cf34952a

Local revision number 85168
"""

Two options, remove the link or update the site.