Allow for course subscriptions

lms/djangoapps/django_comment_client/permissions.py

@@ -5,7 +5,8 @@ from student.models import CourseEnrollment
 
 import logging
 from util.cache import cache
-
+from django.core import cache
+cache = cache.get_cache('default')
 
 def cached_has_permission(user, permission, course_id=None):
     """

lms/lib/comment_client/user.py

@@ -8,7 +8,8 @@ class User(models.Model):
     accessible_fields = ['username', 'email', 'follower_ids', 'upvoted_ids', 'downvoted_ids',
                          'id', 'external_id', 'subscribed_user_ids', 'children', 'course_id',
                          'subscribed_thread_ids', 'subscribed_commentable_ids',
-                         'subscribed_course_ids', 'threads_count', 'comments_count', 'default_sort_key'
+                         'subscribed_course_ids', 'threads_count', 'comments_count', 
+                         'default_sort_key'
                         ]
 
     updatable_fields = ['username', 'external_id', 'email', 'default_sort_key']