ensure ccpo review fields are optional, add form error alert to review screen

templates/requests/approval.html

@@ -8,6 +8,13 @@
 
 <article class='col col--grow request-approval'>
 
+{% if f.errors %}
+  {{ Alert('There were some errors',
+    message="<p>Please see below.</p>",
+    level='error'
+  ) }}
+{% endif %}
+
   <form method="POST" action="{{ url_for("requests.submit_approval", request_id=request_id) }}" autocomplete="off">
     {{ f.csrf_token }}
     <section class='panel'>