Squashed 'nix/nixpkgs/' changes from 7e15417e423..2ff7ef373e5
Squashed 'nix/nixpkgs/' changes from 7e15417e423..2ff7ef373e5

2ff7ef373e5 youtube-dl: 2019.01.17 -> 2019.01.30.1 (#55076)

git-subtree-dir: nix/nixpkgs
git-subtree-split: 2ff7ef373e50c220f824d04a3bb5b819c3484b12

maximilianhuber/myconfig,maximilianhuber/myconfig,maximilianhuber/myconfig,maximilianhuber/myconfig