Unable to update to ros_melodic

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I get the following error when I try to run the command:

sudo apt-get install ros-melodic-desktop-full

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:
 gsettings-desktop-schemas : Breaks: mutter (< 3.19.92) but 3.18.3-0ubuntu2 is to be installed
 ros-melodic-desktop-full : Depends: ros-melodic-desktop but it is not going to be installed
                            Depends: ros-melodic-perception but it is not going to be installed
                            Depends: ros-melodic-simulators but it is not going to be installed
                            Depends: ros-melodic-urdf-sim-tutorial but it is not going to be installed
E: Error, pkgProblemResolver::Resolve generated breaks, this may be caused by held packages.

What is the gsettings-desktop-schemas?