Added an sr-only alert to the site for upload errors (and any other errors we might want to only announce to the screen reader)

app/templates/components/banner.html

@@ -4,10 +4,6 @@
 {% macro banner(body, type=None, with_tick=False, delete_button=None, subhead=None, context=None, action=None, id=None, thing=None) %}
   <div
     class='banner{% if type %}-{{ type }}{% endif %}{% if with_tick %}-with-tick{% endif %}'
-    {% if type == 'dangerous' %}
-    role='group'
-    tabindex='-1'
-    {% endif %}
     {% if id %}
     id={{ id }}
     {% endif %}