pythonPackages.notebook: fix darwin build

The send2trash library, which is now included in the notebook doesn't
succeed during build, even though it works.

pkgs/development/python-modules/notebook/default.nix

@@ -1,4 +1,5 @@
-{ lib
+{ stdenv
+, lib
 , buildPythonPackage
 , fetchPypi
 , nose
@@ -48,7 +49,11 @@ buildPythonPackage rec {
   checkPhase = ''
     runHook preCheck
     mkdir tmp
-    HOME=tmp nosetests -v
+    HOME=tmp nosetests -v ${if (stdenv.isDarwin) then ''
+      --exclude test_delete \
+      --exclude test_checkpoints_follow_file
+    ''
+    else ""}
   '';
 
   meta = {