add a finally statement to be sure to turn back on event firing on writes in…

add a finally statement to be sure to turn back on event firing on writes in case an import throws an exception

common/lib/xmodule/xmodule/modulestore/xml_importer.py

@@ -207,6 +207,7 @@ def import_from_xml(store, data_dir, course_dirs=None,
             course_id_components = course_id.split('/')
             pseudo_course_id = '/'.join([course_id_components[0], course_id_components[1]])
 
+        try:
             # turn off all write signalling while importing as this is a high volume operation
             if pseudo_course_id not in store.ignore_write_events_on_courses:
                 store.ignore_write_events_on_courses.append(pseudo_course_id)
@@ -305,7 +306,7 @@ def import_from_xml(store, data_dir, course_dirs=None,
                 # NOTE: It's important to use own_metadata here to avoid writing
                 # inherited metadata everywhere.
                 store.update_metadata(module.location, dict(own_metadata(module)))
-
+        finally:
             # turn back on all write signalling
             if pseudo_course_id  in store.ignore_write_events_on_courses:
                 store.ignore_write_events_on_courses.remove(pseudo_course_id)