greenlight/app/views/errors/unprocessable.html.erb

<div class="text-center center-page">
  <h1 class="display-2 font-weight-400">Oops!</h1>
  <h3>Request is unprocessable.</h3>
  <%= link_to root_url do %>
    <h4>Return to home page.</h4>
  <% end %>
</div>