deprecation warning on Python 3.11: 'cgi' is deprecated and slated for removal in Python 3.13

[jugmac00]

.tox/py311/lib/python3.11/site-packages/testtools/testresult/real.py:25
  /home/jugmac00/Projects/lpcraft/.tox/py311/lib/python3.11/site-packages/testtools/testresult/real.py:25: DeprecationWarning: 'cgi' is deprecated and slated for removal in Python 3.13
    import cgi

Also see:
https://peps.python.org/pep-0594/#cgi

And yes I know - it will take a couple of years until anybody will use 3.14 :-)

[cjwatson]

Fixed in #340.