This reverts commit aab534b894 & uses the
driverInteractive attribute for the test driver instead.
This has the same effect but removes the extra module in the
nixos-build-vms code.
When I test a change e.g. in the module system manually, I usually use
`nixos-build-vms(8)` which also gives me a QEMU window where I can play
around in the freshly built VM.
It seems as this has changed recently when the default package for
non-interactive VM tests using the same framework was switched to
`pkgs.qemu_test` to reduce the closure size. While this is a reasonable
decision for our CI tests, I think that you really want a QEMU window of
the VM by default when using `nixos-build-vms(8)`.
[1] bc2188b083
When trying to build a VM using `nixos-build-vms` with a configuration
that doesn't evaluate, an error "at `<unknown-file>`" is usually shown.
This happens since the `build-vms.nix` creates a VM-network of
NixOS-configurations that are attr-sets or functions and don't contain
any file information. This patch manually adds the `_file`-attribute to
tell the module-system which file contained broken configuration:
```
$ cat vm.nix
{ vm.invalid-option = 1; }
$ nixos-build-vms vm.nix
error: The option `invalid-option' defined in `/home/ma27/Projects/nixpkgs/vm.nix@node-vm' does not exist.
(use '--show-trace' to show detailed location information)
```
In 0945178b3c we decided that Perl-based
VM tests should be deprecated and will be removed between 20.03 and
20.09. So let's switch `nixos-build-vms(8)` to python as well (which is
entirely interactive, so other scripts won't break).
In my experience, the test-driver isn't used most of the time, so this
patch is mainly supposed to get rid of the (probably misleading)
deprecation warning when running `nixos-build-vms`. Apart from that, the
interface for python's test-driver is way nicer.
Previously I got the following error message:
```
error: opening file '/home/ma27/Projects/nixpkgs/nixos/modules/installer/default.nix': No such file or directory
```
Probably related to 6c68fbd4e1.
