Comment 12 for bug 875440

Otlay's workaround worked for me. But I had to go through some pushups to get it installed without error. I had a dependency conflict with some :i386 packages.

My procedure was to first turn off the sasl daemon:

sudo /etc/init.d/saslauthd stop

...then remove the existing packages:

sudo dpkg -r libsasl2-dev
sudo dpkg -r libsasl2-modules-sql
sudo dpkg -r sasl2-bin
sudo dpkg -r --force-all libsasl2-2 libsasl2-2:i386
sudo dpkg -r --force-all libsasl2-modules

...and install the older packages:

sudo dpkg -i --force-all libsasl2-modules-sql_2.1.23.dfsg1-5ubuntu3_amd64.deb libsasl2-dev_2.1.23.dfsg1-5ubuntu3_amd64.deb sasl2-bin_2.1.23.dfsg1-5ubuntu3_amd64.deb

...restart:

sudo /etc/init.d/saslauthd restart
sudo /etc/init.d/postfix restart

Note: I think any other updates are on hold until this gets resolved.

e.g.:

sudo apt-get install gnome-tweak-tool

Reading package lists... Done
Building dependency tree
Reading state information... Done
You might want to run 'apt-get -f install' to correct these:
The following packages have unmet dependencies:
 gnome-tweak-tool : Depends: gnome-shell but it is not going to be installed
 libldap-2.4-2:i386 : Depends: libsasl2-2:i386 but it is not going to be installed
E: Unmet dependencies. Try 'apt-get -f install' with no packages (or specify a solution).