I/O operation on closed file.: ValueError
Traceback (most recent call last):
  File "/var/task/index.py", line 40, in handler
    ffmpegCombine()
  File "/var/task/index.py", line 51, in ffmpegCombine
    utils.command(['./ffmpeg', '-i', 'concat:./1.mp3|./2.mp3', '-acodec', 'copy', './3.mp3'], timeout=15)
  File "/var/task/utilities/utils.py", line 259, in command
    return p.returncode, p.stdout.readlines()
ValueError: I/O operation on closed file.