update-alternatives error on firefox install

[Mike Hommey]

On Mon, Mar 28, 2016 at 08:16:33PM +0200, Pierre Frenkiel wrote:
> hi,
> Up to now, I was using the iceweasel provided by the Debian Jessie repository.
> Today, I found in your site (http://mozilla.debian.net/)
> 
>      WARNING: Iceweasel is gone. Please update your apt sources.
> 
> So, I followed this instructions, choosing to install Firefox, version release.
> 
> but  apt-get install -t jessie-backports firefox
> gave;
>  update-alternatives: error: alternative path /usr/bin/firefox doesn't exist
> 
> which was true: /usr/bin/firefox was actually missing.

How can it be missing? It's in the package!

$ dpkg -c firefox_45.0.1-1~bpo80+1_amd64.deb  | grep usr/bin
drwxr-xr-x root/root         0 2016-03-19 12:50 ./usr/bin/
lrwxrwxrwx root/root         0 2016-03-19 12:50 ./usr/bin/firefox -> ../lib/firefox/firefox