building Nix...
building the system configuration...
these derivations will be built:
  /nix/store/pqn4w7l4w5504axdgy0wj6ajl7knah40-test-environment.drv
  /nix/store/ijr5d22hfd2qpfnxxlw3l7k0fp8h0vig-system-path.drv
  /nix/store/d98n7ndgg84zn1fw6glzvipx7409hnrn-dbus-1.drv
  /nix/store/53j3nyknw0a2mxxi52miy9x66046nii2-unit-dbus.service.drv
  /nix/store/i6vgbfq3i5l23b5z45l5hdgi1177b4ki-user-units.drv
  /nix/store/fsva95dlnc980ihrbz84lcykf9jbf3fd-unit-systemd-fsck-.service.drv
  /nix/store/pxsc88h8j5337p8r1jcrlbdcphzp0zbk-unit-polkit.service.drv
  /nix/store/s2c6dnblk4yw6dpb9c59naafwpzj1fcw-unit-dbus.service.drv
  /nix/store/r1ykfc2g6v23npn5i9pvanl52cpcr8d8-system-units.drv
  /nix/store/cv3knmkxgl9j5pvihmqi39816dybc1an-etc.drv
  /nix/store/87siv7xsn7b9yir7mqbf5s9gxlhsp9ad-nixos-system-nixos-19.09.2163.d0b3ab3b249.drv
building '/nix/store/pqn4w7l4w5504axdgy0wj6ajl7knah40-test-environment.drv'...
unpacking sources
variable $src or $srcs should point to the source
builder for '/nix/store/pqn4w7l4w5504axdgy0wj6ajl7knah40-test-environment.drv' failed with exit code 1
cannot build derivation '/nix/store/ijr5d22hfd2qpfnxxlw3l7k0fp8h0vig-system-path.drv': 1 dependencies couldn't be built
cannot build derivation '/nix/store/87siv7xsn7b9yir7mqbf5s9gxlhsp9ad-nixos-system-nixos-19.09.2163.d0b3ab3b249.drv': 1 dependencies couldn't be built
error: build of '/nix/store/87siv7xsn7b9yir7mqbf5s9gxlhsp9ad-nixos-system-nixos-19.09.2163.d0b3ab3b249.drv' failed