configparser breaks on duplicate sections

[myoung34]

$ poetry run tilty -c config.ini
Traceback (most recent call last):
  File "/home/myoung/.cache/pypoetry/virtualenvs/tilty-2nsyYZ1s-py3.7/bin/tilty", line 33, in <module>
    sys.exit(load_entry_point('Tilty', 'console_scripts', 'tilty')())
  File "/home/myoung/.cache/pypoetry/virtualenvs/tilty-2nsyYZ1s-py3.7/lib/python3.7/site-packages/click/core.py", line 829, in __call__
    return self.main(*args, **kwargs)
  File "/home/myoung/.cache/pypoetry/virtualenvs/tilty-2nsyYZ1s-py3.7/lib/python3.7/site-packages/click/core.py", line 782, in main
    rv = self.invoke(ctx)
  File "/home/myoung/.cache/pypoetry/virtualenvs/tilty-2nsyYZ1s-py3.7/lib/python3.7/site-packages/click/core.py", line 1066, in invoke
    return ctx.invoke(self.callback, **ctx.params)
  File "/home/myoung/.cache/pypoetry/virtualenvs/tilty-2nsyYZ1s-py3.7/lib/python3.7/site-packages/click/core.py", line 610, in invoke
    return callback(*args, **kwargs)
  File "/home/myoung/repos/github/tilty/tilty/cli.py", line 66, in run
    CONFIG.read(config_file)
  File "/home/myoung/.asdf/installs/python/3.7.2/lib/python3.7/configparser.py", line 696, in read
    self._read(fp, filename)
  File "/home/myoung/.asdf/installs/python/3.7.2/lib/python3.7/configparser.py", line 1065, in _read
    lineno)
configparser.DuplicateSectionError: While reading from 'config.ini' [line 18]: section 'webhook' already exists