Showing \"/Users/Christian/Desktop/sample_app/app/views/layouts/application.html.erb\" where line #5 raised:
No such file or directory - /Users/Christ
Change sass-rails version to 4.0.3 and leave the rest as it is. Remove Gemfile.lock when necessary, and then:
$ bundle update
$ bundle install
Finally, don't forget to restart your rails server!
In your Gemfile change the sass-rails version to 4.0.3. Get rid of a version number for sprockets. Delete the Gemfile.lock. Run the bundle install again