update-maintainer failed

Binary package hint: python-debian

On package defoma (from Debian unstable) I run script update-maintainer from package ubuntu-dev-tools.

$ update-maintainer
The original maintainer is: Debian QA Group <email address hidden>
Resetting as: Ubuntu Developers <email address hidden>
Traceback (most recent call last):
  File "/usr/bin/update-maintainer", line 43, in <module>
    main()
  File "/usr/bin/update-maintainer", line 40, in main
    sys.exit(update_maintainer(options.debian_directory, not options.quiet))
  File "/usr/lib/python2.7/dist-packages/ubuntutools/update_maintainer.py", line 102, in update_maintainer
    control.save()
  File "/usr/lib/python2.7/dist-packages/ubuntutools/control.py", line 61, in save
    content = u"\n".join([x.dump() for x in self.paragraphs])
  File "/usr/lib/pymodules/python2.7/debian/deb822.py", line 406, in dump
    value = self.get_as_string(key)
  File "/usr/lib/pymodules/python2.7/debian/deb822.py", line 381, in get_as_string
    return unicode(self[key])
  File "/usr/lib/pymodules/python2.7/debian/deb822.py", line 178, in __getitem__
    value = self.__parsed[key]
  File "/usr/lib/pymodules/python2.7/debian/deb822.py", line 62, in __getitem__
    raise KeyError(key)
KeyError: '# dfontmgr is a GUI frontend for Defoma. You can see the fonts registered\n'