Example:
% sudo apt-get build-dep emacs25
Reading package lists... Done
E: Unable to find a source package for emacs25
I have run `apt-get update` before running the command above, and my
`/etc/apt/sources.list` file contains the following
deb http://deb.debian.org/debian stretch main contrib non-free
deb-src http://deb.debian.org/debian stretch main contrib non-free
deb http://deb.debian.org/debian stretch-updates main contrib non-free
deb-src http://deb.debian.org/debian stretch-updates main contrib
non-free
deb http://security.debian.org/ stretch/updates main contrib non-free
deb-src http://security.debian.org/ stretch/updates main contrib
non-free
What am I doing wrong?
