erp5_corporate_identity: handle missing images explicitly

bt5/erp5_corporate_identity/SkinTemplateItem/portal_skins/erp5_corporate_identity/WebPage_validateImage.py

@@ -12,6 +12,7 @@ Upgrade image for the specific type of display
 # img_svg_format                display image as svg (default png/None)
 
 import re
+from OFS.Traversable import NotFound
 
 if img_string == None or img_string == "":
   return img_string
@@ -20,8 +21,9 @@ img_src = re.findall("src=['\"](.*?)['\"]", img_string)[0]
 img_obj = context.restrictedTraverse(img_src.split("?")[0])
 img_type = img_obj.getContentType()
 
-# XXX flag broken link
-# if img_obj is None:
+# flag broken link until further notice
+if img_obj is None:
+  raise NotFound('The following image could not be found in erp5: %s' % (img_src.split("?")[0]))
 
 # ensure alt attributes are set
 if img_string.find('alt=') == -1: