update-maintainer needlessly reads entire control file and can explode

Binary package hint: ubuntu-dev-tools

update-maintainer does not work on some control files. For example, Karmic's exim4 package:

$ update-maintainer
The old maintainer was: Ubuntu Core Developers <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 79, 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: '# psmisc just for exiwhat.\n'

ProblemType: Bug
DistroRelease: Ubuntu 11.04
Package: ubuntu-dev-tools 0.114
ProcVersionSignature: Ubuntu 2.6.37-12.26-generic 2.6.37
Uname: Linux 2.6.37-12-generic x86_64
Architecture: amd64
Date: Tue Feb 8 11:12:47 2011
PackageArchitecture: all
ProcEnviron:
 LANGUAGE=en_US:en
 PATH=(custom, user)
 LANG=en_US.UTF-8
 LC_MESSAGES=en_US.utf8
 SHELL=/bin/bash
SourcePackage: ubuntu-dev-tools