Comment 1 for bug 135179

Thanks for your comments. This does not appear to be a bug report and are closing it. We appreciate the difficulties you are facing, but it would make more sense to raise your question in the support tracker - http://launchpad.net/support .

The brother drivers looks really bad, you could try to run:
$ sudo rm /var/lib/dpkg/info/mfc8420lpr.postrm
$ sudo apt-get remove mfc8500lpr mfc8420lpr