a11yist/app/views/layouts/_flash.html.erb

<% if flash[:alert] || flash[:notice] %>
  <% if flash[:alert] %>
    <div class="alert alert-danger" role="alert">
      <%= flash[:alert] %><% flash.delete(:alert) %>
    </div>
  <% end %>

  <% if flash[:notice] %>
    <div class="alert alert-info" role="alert">
      <%= flash[:notice] %>
      <% flash.delete(:notice) %>
    </div>
  <% end %>
<% end %>