Answer by Chaudhary Prakash for Error while installing ruby using rvm

I had the above error on installing ruby-2.3.0 in Ubuntu 16.04.

Go to the file:

/etc/apt/sources.list.d/mc3man-ubuntu-trusty-media-xenial.list

and remove the below:

deb-src http://ppa.launchpad.net/mc3man/trusty-media/ubuntu xenial maindeb http://ppa.launchpad.net/mc3man/trusty-media/ubuntu xenial main 

then run sudo apt-get update and after rvm install ruby-2.3.0 it's working.