Hide submit button after student submits

common/lib/xmodule/xmodule/js/src/combinedopenended/display.coffee

@@ -375,6 +375,7 @@ class @CombinedOpenEnded
 
   save_answer: (event) =>
     event.preventDefault()
+    @submit_button.hide()
     max_filesize = 2*1000*1000 #2MB
     pre_can_upload_files = @can_upload_files
     if @child_state == 'initial'

common/lib/xmodule/xmodule/open_ended_grading_classes/openendedchild.py

@@ -182,7 +182,7 @@ class OpenEndedChild(object):
                               whitelist_tags=set(['embed', 'iframe', 'a', 'img']))
             clean_html = cleaner.clean_html(answer)
             clean_html = re.sub(r'</p>$', '', re.sub(r'^<p>', '', clean_html))
-        except:
+        except Exception:
             clean_html = answer
         return clean_html