Since my sudo apt-get upgrade today I have this weird error(s) in the end of each software installation with apt-get, for instance :

    $apt-get -f install 

Reading package lists... Done

Building dependency tree       

Reading state information... Done

Correcting dependencies... Done

The following packages were automatically installed and are no longer required:

  liblzo2-2 uswsusp

Use 'apt-get autoremove' to remove them.

The following extra packages will be installed:

  libglu1-mesa

The following NEW packages will be installed:

  libglu1-mesa

0 upgraded, 1 newly installed, 0 to remove and 10 not upgraded.

1 not fully installed or removed.

Need to get 0 B/165 kB of archives.

After this operation, 561 kB of additional disk space will be used.

Do you want to continue [Y/n]? Y

Selecting previously deselected package libglu1-mesa.

(Reading database ... 140491 files and directories currently installed.)

Unpacking libglu1-mesa (from .../libglu1-mesa_7.10.2-0ubuntu2.1_amd64.deb) ...

Setting up libgl1-mesa-glx (7.10.2-0ubuntu2.1) ...

update-alternatives: error: alternative link /usr/lib/xorg/extra-modules is already managed by x86_64-linux-gnu_gl_conf.

dpkg: error processing libgl1-mesa-glx (--configure):

 subprocess installed post-installation script returned error exit status 2

dpkg: dependency problems prevent configuration of libglu1-mesa:

 libglu1-mesa depends on libgl1-mesa-glx | libgl1; however:

  Package libgl1-mesa-glx is not configured yet.

  Package libgl1 is not installed.

  Package libgl1-mesa-glx which provides libgl1 is not configured yet.

dpkg: error processing libglu1-mesa (--configure):

 dependency problems - leaving unconfigured

No apport report written because the error message indicates its a followup error from a previous failure.

                          Errors were encountered while processing:

 libgl1-mesa-glx

 libglu1-mesa

E: Sub-process /usr/bin/dpkg returned an error code (1)

Does anyone know how to repair that ? I have tried apt-get purge or apt-get install on 'these' packages back did not help.