add disclaimer for subscription purchase with AE account

core/templates/core/group_detail.jinja

@@ -15,6 +15,7 @@
       {{ select_all_checkbox("add_users") }}
       <hr>
       {% csrf_token %}
+      {{ form.non_field_errors() }}
       <label for="{{ form.users_removed.id_for_label }}">{{ form.users_removed.label }} :</label>
       {{ form.users_removed.errors }}
       {% for user in form.users_removed %}