Add coverage for rescue from CanCan AccessDenied
user
```ruby
require 'spec_helper'

feature "Access Denied" do
  before do
    @user = FactoryGirl.create(:user)
    @institution = FactoryGirl.create(:institution)
  end

  scenario "Unauthorized user tries to view page" do
    login_as(@user)

    # Visit the path of an institution that is not the user's
    visit(institution_path(@institution))
    
    expect(page).to have_content "You are not authorized to access this page."
    current_path.should == root_path
  end
end```
assistant