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:
libreoffice : Depends: libreoffice-base but it is not going to be
installed
           Depends: libreoffice-calc but it is not going to be
installed
           Depends: libreoffice-core (= 1:5.1.6~rc2-0ubuntu1~xenial2)
but it is not going to be installed
           Depends: libreoffice-draw but it is not going to be
installed
           Depends: libreoffice-impress but it is not going to be
installed
           Depends: libreoffice-math but it is not going to be
installed
           Depends: libreoffice-report-builder-bin but it is not going
to be installed
           Depends: libreoffice-writer but it is not going to be
installed
           Depends: libreoffice-avmedia-backend-gstreamer but it is
not going to be installed
           Depends: python3-uno (>= 4.4.0~beta2) but it is not going
to be installed
E: Unable to correct problems, you have held broken packages.