Comment 2 for bug 630643

The problem is here:

update-alternatives: error: alternative path /usr/bin/firefox doesn't exist.
dpkg: error processing firefox (--configure):
 subprocess installed post-installation script returned error exit status 2

That's not our bug. The issue is that some third-party package you have installed has diverted that link (most likely Ubuntuzilla). Please report your bug to them instead