fix: add logger warning for dupe

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

@@ -68,9 +68,15 @@ def add_course_staff_from_csv(self, csv_file, batch_size, batch_delay):
         for i in range(0, len(reader), batch_size):
             users_list = []
             for row in reader[i:i + batch_size]:
+                username = row.get('username')
+                email = row.get('email')
                 try:
                     users_list.append(User.objects.get_or_create(username=row.get('username'), email=row.get('email')))
                 except IntegrityError:
+                    logger.warning(
+                        f'User with username={username} and email={email} was not created due to an existing duplicate '
+                        f'user with username.'
+                    )
                     continue
             users_dict = dict([(u.username, u) for (u, c) in users_list])
             users.update(users_dict)