Fix spec by not raising the error image not found

`GET http://localhost:3000/throbber.gif 404 (Not Found)`

In the meantime, open an issue to remove jquery.jstree from this page: 9677

spec/system/admin/configuration/taxonomies_spec.rb

@@ -43,6 +43,10 @@ describe "Taxonomies" do
   end
 
   context "edit" do
+    before do
+      Capybara.raise_server_errors = false
+    end
+
     it "should allow an admin to update an existing taxonomy" do
       create(:taxonomy)
       click_link "Taxonomies"