views: Make set boot-mode more robust

Check that server replies with error code and display an error if it
does.

ogcp/views.py

@@ -1211,6 +1211,10 @@ def action_mode():
         server = get_server_from_clients(ips)
         modes_set = get_clients_modes(ips, server)
         r = server.get('/mode')
+        if r.status_code != requests.codes.ok:
+            flash(_('Ogserver replied with status code not ok'),
+                  category='error')
+            return redirect(url_for('commands'))
         available_modes = [(mode, mode) for mode in r.json()['modes']]
         form.boot.choices = list(available_modes)