Let dmd or ldc be easy to setup on Ubuntu

[FrankLike via Digitalmars-d-learn]

Now,we can't setup dmd or ldc like this:
 sudo apt-get install dmd
 sudo apt-get install ldc2

If I set 'The Installation Source' is :
deb http://downloads.dlang.org/releases/2015/ main

But it's error,why?

Thank you.