error

sudo apt-get install gnome-session-fallback

Reading package lists... Done

Building dependency tree      

Reading state information... Done

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.

 gnome-session-fallback : Depends: gnome-session-flashback but it is not going to be installed

E: Unable to correct problems, you have held broken packages.