Increase the visibility of "No packages found."

src/Packagist/WebBundle/Resources/views/Web/list.html.twig

@@ -9,7 +9,9 @@
         {% if packages|length %}
             {{ macros.listPackages(packages, paginate is not defined or paginate, showAutoUpdateWarning|default(false), meta|default(null)) }}
         {% else %}
-            <p>No packages found.</p>
+            <div class="alert alert-danger">
+                <p>No packages found.</p>
+            </div>
         {% endif %}
     {% endblock %}
 {% endblock %}