nixos/tests: format the testing-python.nix file more consistenly

nixos/lib/testing-python.nix

@@ -7,7 +7,8 @@
   # !!! See comment about args in lib/modules.nix
 , specialArgs ? { }
   # Modules to add to each VM
-, extraConfigurations ? [] }:
+, extraConfigurations ? [ ]
+}:
 
 with pkgs;
 
@@ -16,9 +17,11 @@ rec {
   inherit pkgs;
 
 
-  mkTestDriver = let
+  mkTestDriver =
+    let
       testDriverScript = ./test-driver/test-driver.py;
-  in qemu_pkg: stdenv.mkDerivation {
+    in
+    qemu_pkg: stdenv.mkDerivation {
       name = "nixos-test-driver";
 
       nativeBuildInputs = [ makeWrapper ];
@@ -75,7 +78,6 @@ rec {
     , skipLint ? false
     , ...
     } @ t:
-
     let
       # A standard store path to the vm monitor is built like this:
       #   /tmp/nix-build-vm-test-run-$name.drv-0/vm-state-machine/monitor
@@ -108,7 +110,8 @@ rec {
           testDriver = mkTestDriver (if qemu_pkg == null then pkgs.qemu_test else qemu_pkg);
 
           nodes = build-vms.buildVirtualNetwork (
-            t.nodes or (if t ? machine then { machine = t.machine; } else { }));
+            t.nodes or (if t ? machine then { machine = t.machine; } else { })
+          );
           vlans = map (m: m.config.virtualisation.vlans) (lib.attrValues nodes);
           vms = map (m: m.config.system.build.vm) (lib.attrValues nodes);
 
@@ -120,7 +123,8 @@ rec {
 
           testDriverName = with builtins;
             if testNameLen > maxTestNameLen then
-              abort ("The name of the test '${name}' must not be longer than ${toString maxTestNameLen} " +
+              abort
+                ("The name of the test '${name}' must not be longer than ${toString maxTestNameLen} " +
                   "it's currently ${toString testNameLen} characters long.")
             else
               "nixos-test-driver-${name}";
@@ -128,7 +132,8 @@ rec {
           warn = if skipLint then lib.warn "Linting is disabled!" else lib.id;
         in
         warn (runCommand testDriverName
-        { buildInputs = [ makeWrapper];
+          {
+            buildInputs = [ makeWrapper ];
             testScript = testScript';
             preferLocalBuild = true;
             testName = name;
@@ -172,7 +177,8 @@ rec {
 
       nodeNames = builtins.attrNames driver.nodes;
       invalidNodeNames = lib.filter
-        (node: builtins.match "^[A-z_]([A-z0-9_]+)?$" node == null) nodeNames;
+        (node: builtins.match "^[A-z_]([A-z0-9_]+)?$" node == null)
+        nodeNames;
 
     in
     if lib.length invalidNodeNames > 0 then
@@ -202,8 +208,10 @@ rec {
       };
 
       vm = build-vms.buildVM { }
-        [ machine
-          { key = "run-in-machine";
+        [
+          machine
+          {
+            key = "run-in-machine";
             networking.hostName = "client";
             nix.readOnlyStore = false;
             virtualisation.writableStore = false;