[Qgis-user] QGIS 2.12 unmet dependencies in Ubuntu

[Martin Pescador]

Hello

I am trying to install QGIS 2.12 on Ubuntu 15.10. I have uninstalled a 
previous version of Ubuntu and followed the instructions at 
http://qgis.org/en/site/forusers/alldownloads.html#debian-ubuntu (i.e. I 
have added the repository for the release with ubuntugis dependencies 
and have added the two required debs to /etc/apt/sources.list

Following 'sudo apt-get install qgis python-qgis qgis-plugin-grass' the 
message is

'Package qgis-plugin-grass is not available, but is referred to by 
another package. This may mean that the package is missing, has been 
obsoleted, or is only available from another source.'

Then trying with only 'sudo apt-get install qgis python-qgis' the 
following is output:

Reading package lists... Done
Building dependency tree
Reading state information... Done
python-qgis is already the newest version.
Some packages could not be installed. This may mean that you have
requested an impossible situation or if you are using the unstable
distribution that some required packages have not yet been created
or been moved out of Incoming.
The following information may help to resolve the situation:

The following packages have unmet dependencies.
  qgis : Depends: libgdal1i (>= 1.8.0) but it is not going to be installed
         Depends: libgeos-c1v5 (>= 3.4.2) but it is not going to be 
installed
         Depends: libqgis-analysis2.8.3 (>= 2.0.1) but it is not going 
to be installed
         Depends: libqgis-core2.8.3 (>= 2.8.3) but it is not going to be 
installed
         Depends: libqgis-gui2.8.3 (>= 2.8.1) but it is not going to be 
installed
         Depends: libqgis-networkanalysis2.8.3 (>= 2.0.1) but it is not 
going to be installed
         Depends: libspatialite7 (>= 2.4.0) but it is not going to be 
installed
         Depends: python-qgis (= 2.8.3+dfsg-1) but 1:2.10.1+20trusty is 
to be installed
         Depends: qgis-providers (= 2.8.3+dfsg-1) but it is not going to 
be installed
         Recommends: qgis-plugin-globe but it is not going to be installed
E: Unable to correct problems, you have held broken packages.

If anybody could advise, I would be grateful.

Thanks, Martin