add flash meesage into layout

backstage/templates/layout.html

@@ -143,6 +143,18 @@
 
     <!-- MAIN -->
     <div class="col">
+        <div class="col-md-8">
+          {% with messages = get_flashed_messages(with_categories=true) %}
+            {% if messages %}
+              {% for category, message in messages %}
+                <div class="alert alert-{{ category }}">
+                  {{ message }}
+                </div>
+              {% endfor %}
+            {% endif %}
+          {% endwith %}
+          {% block content %}{% endblock %}
+        </div>
       {% block main %}{% endblock %}
     </div><!-- Main Col END -->
   </div><!-- body-row END -->