Run

gksu gedit /etc/*release

Change the file like this (depending on your release):

DISTRIB_ID=Ubuntu DISTRIB_RELEASE=16.04 DISTRIB_CODENAME=Xenial Xerus DISTRIB_DESCRIPTION="Ubuntu 16.04"

Save and close the file. - Run

gksu gedit /etc/*issue

Change the file like this (depending on your release):

Ubuntu 16.04 \n \l

Save and close the file. - sudo apt-get install --reinstall software-center