01174c5f4d
Before this patch, a VM was used to spawn docker that pulled the VM. Now, the tool Skopeo does this job well so we can simplify our dockerTools since we doesn't need Docker anymore:) This also fixe the regression described in https://github.com/NixOS/nixpkgs/issues/29271 : cntlm proxy doesn't work in 17.09 while it worked in 17.03. Note Skopeo doesn't produce the same output than docker pull so, we have to update sha.