# Pastebin FtnTE9f8
nix-build -E 'with import <nixpkgs> { system = "x86_64-linux"; }; runCommand "foo" {} "uname -a"'
these derivations will be built:
  /nix/store/fk01iaghsfl7vr5rbg0pkyfc5afk1ibc-foo.drv
these paths will be fetched (0.01 MiB download, 0.04 MiB unpacked):
  /nix/store/71vam18l4f9dqsr1j3b327vny0brw4l0-stdenv
fetching path ‘/nix/store/71vam18l4f9dqsr1j3b327vny0brw4l0-stdenv’...

*** Downloading ‘https://cache.nixos.org/nar/0hykryny62fq2gbk4hfix3sp3ma6l8ypsi6gisdj36iqy4kx9m3y.nar.xz’ (signed by ‘cache.nixos.org-1’) to ‘/nix/store/71vam18l4f9dqsr1j3b327vny0brw4l0-stdenv’...
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
100 10716  100 10716    0     0  10716      0  0:00:01 --:--:--  0:00:01 14719

copying 206 missing paths (48.99 MiB) to ‘root@nix-docker’...
building ‘/nix/store/fk01iaghsfl7vr5rbg0pkyfc5afk1ibc-foo.drv’ on ‘root@nix-docker’
Linux 9de09a394d25 4.9.60-linuxkit-aufs #1 SMP Mon Nov 6 16:00:12 UTC 2017 x86_64 GNU/Linux
builder for ‘/nix/store/fk01iaghsfl7vr5rbg0pkyfc5afk1ibc-foo.drv’ failed to produce output path ‘/nix/store/sb7hfx51nmwgj2yzsxd0lys54b566n2x-foo’
error: build of ‘/nix/store/fk01iaghsfl7vr5rbg0pkyfc5afk1ibc-foo.drv’ failed on ‘root@nix-docker’
error: build of ‘/nix/store/fk01iaghsfl7vr5rbg0pkyfc5afk1ibc-foo.drv’ failed