nixos/tests: fix #146169

nixos/lib/testing-python.nix

@@ -51,6 +51,7 @@ rec {
     , enableOCR ? false
     , skipLint ? false
     , passthru ? {}
+    , interactive ? false
   }:
     let
       # Reifies and correctly wraps the python test driver for
@@ -139,7 +140,8 @@ rec {
         wrapProgram $out/bin/nixos-test-driver \
           --set startScripts "''${vmStartScripts[*]}" \
           --set testScript "$out/test-script" \
-          --set vlans '${toString vlans}'
+          --set vlans '${toString vlans}' \
+          ${if interactive then "--add-flags --interactive" else ""}
       '');
 
   # Make a full-blown test
@@ -217,6 +219,7 @@ rec {
         testName = name;
         qemu_pkg = pkgs.qemu;
         nodes = nodes pkgs.qemu;
+        interactive = true;
       };
 
       test =