title: Why is devise not displaying authentication errors on sign in page?
body: <p>I'm using rails 4.2</p>
  
  <p>I have a helper file called devise_helper.rb </p>
  
  <pre><code>module DeviseHelper
      def devise_error_messages!
          return "" if resource.errors.empty?
  
      messages = resource.errors.full_messages.map { |msg| content_tag(:li, msg) }.join
      sentence = I18n.t("errors.messages.not_saved",
                    count: resource.errors.count,
                    resource: resource.class.model_name.human.downcase)
  
       html = &lt;&lt;-HTML
       &lt;div class="row"&gt;
       &lt;div class="large-12 columns"&gt;
          &lt;div data-alert class="alert-box alert radius"&gt;
            &lt;h4&gt;#{sentence}&lt;/h4&gt;
            &lt;ul&gt;#{messages}&lt;/ul&gt;
          &lt;/div&gt;
       &lt;/div&gt;
       &lt;/div&gt;
       HTML
       html.html_safe
    end
  end
  </code></pre>
  
  <p>to customize error messages and it's working for registrations and passwords pages, but not for sessions pages. Why is this? I know that I can add something like this:</p>
  
  <pre><code>  &lt;div class="row"&gt;
      &lt;% if notice %&gt;
        &lt;div data-alert class="alert-box info radius"&gt;
          &lt;%= notice %&gt;&lt;%= link_to "X", '#', :class =&gt; 'close' %&gt;
        &lt;/div&gt;
      &lt;% end %&gt;
      &lt;% if alert %&gt;
        &lt;div data-alert class="alert-box alert radius"&gt;
          &lt;%= alert %&gt;&lt;%= link_to "X", '#', :class =&gt; 'close' %&gt;
        &lt;/div&gt;
      &lt;% end %&gt;
    &lt;/div&gt;
  </code></pre>
  
  <p>To my application.html.erb file and error messages will display there, but I don't understand why I have to add that when I have the devise helper already.
  For the passwords and registrations, I just had to add &lt;%= devise_error_messages! %> but the sessions pages don't seem to work that way. I'm not sure if this is just how devise works or if there's something I'm missing.</p>
  
  <p><strong>EDIT:</strong>
  I generated the sessions controller but I never changed anything in it since generating it. From what I understand, devise will just use its default controller until I change the one i generated. My passwords controller is like this as well. I did make some changes to the registrations controller to configure permitted parameters.</p>
  
  <pre><code>class Users::SessionsController &lt; Devise::SessionsController
  
  end
  </code></pre>