docstr: Ensures that when there is an error in the tail_fn (the one that runs in the
  threadpool), it is dealt with and raised properly.
docstr_tok: ["Ensures","that","when","there","is","an","error","in","the","tail_fn","(","the","one","that","runs","in","the","threadpool",")",",","it","is","dealt","with","and","raised","properly","."]
code: def test_tail_logfile_error_in_tail_fn(self, mock_logger):
      """
      Ensures that when there is an error in the tail_fn (the one that runs in the
      threadpool), it is dealt with and raised properly.
      """
  
      # try giving tail log a directory (should fail with an IsADirectoryError
      tail = TailLog(
          "writer", log_files={0: self.test_dir}, dst=sys.stdout
      ).start()
      tail.stop()
  
      mock_logger.error.assert_called_once()
  
imports: import io
  import os
  import shutil
  import sys
  import tempfile
  import time
  import unittest
  from concurrent.futures import wait
  from concurrent.futures._base import ALL_COMPLETED
  from concurrent.futures.thread import ThreadPoolExecutor
  from typing import Dict, Set
  from unittest import mock
  from torch.distributed.elastic.multiprocessing.tail_log import TailLog
label_desc: Use image node_id 7 for calling the TailLogTest obj's underlying member method code with example usage: obj.test_tail_logfile_error_in_tail_fn(mock_logger) without return types