fix: cleanup dict creation

edx_exams/apps/core/management/commands/bulk_add_course_staff.py

@@ -66,7 +66,9 @@ def add_course_staff_from_csv(self, csv_file, batch_size, batch_delay):
         users = {}
 
         for i in range(0, len(reader), batch_size):
-            users_dict = {k: v for k, v in [(u.username, u) for (u, c) in [User.objects.get_or_create(username=row.get('username'), email=row.get('email')) for row in reader[i:i + batch_size]]]}
+            users_dict = dict([(u.username, u) for (u, c)
+                               in [User.objects.get_or_create(username=row.get('username'), email=row.get('email'))
+                                   for row in reader[i:i + batch_size]]])
             users.update(users_dict)
             time.sleep(batch_delay)