cifs-utils: missing python3 dependency for smbinfo

Since cifs-utils 6.12, smbinfo needs Python to be usable.

Issue introduced in 033208fd46.

nixos/tests/cifs-utils.nix

@@ -0,0 +1,12 @@
+import ./make-test-python.nix ({ pkgs, ... }: {
+  name = "cifs-utils";
+
+  machine = { pkgs, ... }: { environment.systemPackages = [ pkgs.cifs-utils ]; };
+
+  testScript = ''
+    machine.succeed("smbinfo -h")
+    machine.succeed("smb2-quota -h")
+    assert "${pkgs.cifs-utils.version}" in machine.succeed("cifs.upcall -v")
+    assert "${pkgs.cifs-utils.version}" in machine.succeed("mount.cifs -V")
+  '';
+})

pkgs/os-specific/linux/cifs-utils/default.nix

@@ -1,5 +1,5 @@
 { stdenv, lib, fetchurl, autoreconfHook, docutils, pkg-config
-, kerberos, keyutils, pam, talloc }:
+, kerberos, keyutils, pam, talloc, python3 }:
 
 stdenv.mkDerivation rec {
   pname = "cifs-utils";
@@ -12,7 +12,7 @@ stdenv.mkDerivation rec {
 
   nativeBuildInputs = [ autoreconfHook docutils pkg-config ];
 
-  buildInputs = [ kerberos keyutils pam talloc ];
+  buildInputs = [ kerberos keyutils pam talloc python3 ];
 
   configureFlags = [ "ROOTSBINDIR=$(out)/sbin" ] ++ lib.optionals (stdenv.hostPlatform != stdenv.buildPlatform) [
     # AC_FUNC_MALLOC is broken on cross builds.