Quadweekly meetings have broken __str__() methods

➜ irc-meetings git:(update-designate-meeting) tox -re ical
ical recreate: /home/graham/repos/github/openstack-infra/irc-meetings/.tox/ical
ical installdeps: -r/home/graham/repos/github/openstack-infra/irc-meetings/test-requirements.txt
ical installed: certifi==2018.4.16,chardet==3.0.4,flake8==2.2.4,hacking==0.10.3,icalendar==4.0.1,idna==2.6,Jinja2==2.10,MarkupSafe==1.0,mccabe==0.2.1,pbr==4.0.3,pep8==1.5.7,pkg-resources==0.0.0,pyflakes==0.8.1,python-dateutil==2.7.3,pytz==2018.4,PyYAML==3.12,requests==2.18.4,six==1.11.0,urllib3==1.22,yaml2ical==0.8.0
ical runtests: PYTHONHASHSEED='3065456237'
ical runtests: commands[0] | mkdir -p output/calendars
ical runtests: commands[1] | yaml2ical -n OpenStack Meetings -d Meeting schedule for the OpenStack projects -y meetings -o output/irc-meetings.ical -t meetingindex.jinja -w output/index.html -f
2018-05-15 14:45:09,352 - INFO - Wrote 103 meetings to iCal
Traceback (most recent call last):
  File ".tox/ical/bin/yaml2ical", line 11, in <module>
    sys.exit(main())
  File "/home/graham/repos/github/openstack-infra/irc-meetings/.tox/ical/lib/python3.5/site-packages/yaml2ical/cli.py", line 133, in main
    meetings, index_template, index_output)
  File "/home/graham/repos/github/openstack-infra/irc-meetings/.tox/ical/lib/python3.5/site-packages/yaml2ical/index.py", line 94, in convert_meetings_to_index
    timestamp=datetime.datetime.utcnow()))
  File "/home/graham/repos/github/openstack-infra/irc-meetings/.tox/ical/lib/python3.5/site-packages/jinja2/environment.py", line 1008, in render
    return self.environment.handle_exception(exc_info, True)
  File "/home/graham/repos/github/openstack-infra/irc-meetings/.tox/ical/lib/python3.5/site-packages/jinja2/environment.py", line 780, in handle_exception
    reraise(exc_type, exc_value, tb)
  File "/home/graham/repos/github/openstack-infra/irc-meetings/.tox/ical/lib/python3.5/site-packages/jinja2/_compat.py", line 37, in reraise
    raise value.with_traceback(tb)
  File "/home/graham/repos/github/openstack-infra/irc-meetings/meetingindex.jinja", line 82, in top-level template code
    (IRC <a href="https://webchat.freenode.net/?randomnick=1&channels=%23{{ schedule.irc }}&prompt=1&uio=d4">webclient</a>)
  File "/home/graham/repos/github/openstack-infra/irc-meetings/.tox/ical/lib/python3.5/site-packages/yaml2ical/recurrence.py", line 106, in __str__
    return "Every four weeks" % self.style
AttributeError: 'QuadWeeklyRecurrence' object has no attribute 'style'