Traceback (most recent call last):
  File "/usr/bin/unattended-upgrade", line 1706, in <module>
    main(options)
  File "/usr/bin/unattended-upgrade", line 1610, in main
    options.dry_run)
  File "/usr/bin/unattended-upgrade", line 1262, in do_auto_remove
    res, error = cache_commit(cache, logfile_dpkg, verbose)
  File "/usr/bin/unattended-upgrade", line 475, in cache_commit
    res = cache.commit(install_progress=iprogress)
  File "/usr/lib/python3/dist-packages/apt/cache.py", line 522, in commit
    res = self._fetch_archives(fetcher, pm)
  File "/usr/lib/python3/dist-packages/apt/cache.py", line 348, in _fetch_archives
    raise LockFailedException("Failed to lock %s" % lockfile)
apt.cache.LockFailedException: Failed to lock /var/cache/apt/archives/lock