Just return a null progress if something goes wrong when retrieving capa_module…

Just return a null progress if something goes wrong when retrieving capa_module progress (and log the error)

common/lib/xmodule/xmodule/capa_module.py

@@ -202,10 +202,8 @@ class CapaModule(XModule):
             try:
                 return Progress(score, total)
             except Exception as err:
-                # TODO (vshnayder): why is this still here? still needed?
-                if self.system.DEBUG:
-                    return None
-                raise
+                log.exception("Got bad progress")
+                return None
         return None
 
     def get_html(self):
@@ -322,16 +320,10 @@ class CapaModule(XModule):
 
         before = self.get_progress()
         d = handlers[dispatch](get)
-        try:
-            after = self.get_progress()
-            d.update({
-                'progress_changed': after != before,
-                'progress_status': Progress.to_js_status_str(after),
-                })
-        except ValueError:
-            d.update({
-                'progress_changed': False,
-                'progress_status': Progress.to_js_status(before),
+        after = self.get_progress()
+        d.update({
+            'progress_changed': after != before,
+            'progress_status': Progress.to_js_status_str(after),
             })
         return json.dumps(d, cls=ComplexEncoder)