shuttle: disable buggy test on darwin

(cherry picked from commit ca1921eb5b)

pkgs/tools/security/sshuttle/default.nix

@@ -29,6 +29,10 @@ python3Packages.buildPythonApplication rec {
   # uses Python 3, so it should be fine.
   doCheck = true;
 
+  checkPhase = ''
+    py.test -k "${stdenv.lib.optionalString stdenv.isDarwin "not test_parse_subnetport_ip6"}"
+  '';
+
   postInstall = let
     mapPath = f: x: stdenv.lib.concatStringsSep ":" (map f x);
   in ''