Ignore pylint error 7610 (translation-of-non-string) on where it is intended to do

As some i18n features need ```ugettext``` or its shorcut ```_``` to be called on a non-string-literal, so the pylint check of ```translation-of-non-string``` should be explicitly disabled in such situations.

lms/djangoapps/instructor_task/views.py

@@ -127,7 +127,7 @@ def get_task_completion_info(instructor_task):
         log.warning(fmt.format(instructor_task.task_id, instructor_task.task_output))
         return (succeeded, _("No progress status information available"))
 
-    action_name = _(task_output['action_name'])
+    action_name = _(task_output['action_name'])    # pylint: disable=translation-of-non-string
     num_attempted = task_output['attempted']
     num_total = task_output['total']