gazou export --resume bug

[bmaz]

gazou export --resume -o backup-filter_links_6_part_2.csv --step hours
Traceback (most recent call last):
  File "/home/bma/.pyenv/versions/gazou8/bin/gazou", line 10, in <module>
    sys.exit(main())
  File "/home/bma/.pyenv/versions/3.8.0/envs/gazou8/lib/python3.8/site-packages/click-8.0.0a1-py3.8.egg/click/core.py", line 1025, in __call__
    return self.main(*args, **kwargs)
  File "/home/bma/.pyenv/versions/3.8.0/envs/gazou8/lib/python3.8/site-packages/click-8.0.0a1-py3.8.egg/click/core.py", line 955, in main
    rv = self.invoke(ctx)
  File "/home/bma/.pyenv/versions/3.8.0/envs/gazou8/lib/python3.8/site-packages/click-8.0.0a1-py3.8.egg/click/core.py", line 1517, in invoke
    return _process_result(sub_ctx.command.invoke(sub_ctx))
  File "/home/bma/.pyenv/versions/3.8.0/envs/gazou8/lib/python3.8/site-packages/click-8.0.0a1-py3.8.egg/click/core.py", line 1279, in invoke
    return ctx.invoke(self.callback, **ctx.params)
  File "/home/bma/.pyenv/versions/3.8.0/envs/gazou8/lib/python3.8/site-packages/click-8.0.0a1-py3.8.egg/click/core.py", line 710, in invoke
    return callback(*args, **kwargs)
  File "/home/bma/.pyenv/versions/3.8.0/envs/gazou8/lib/python3.8/site-packages/gazouilloire/cli/__main__.py", line 197, in export
    export_csv(conf, query, exclude_threads, exclude_retweets, since, until,
  File "/home/bma/.pyenv/versions/3.8.0/envs/gazou8/lib/python3.8/site-packages/gazouilloire/exports/export_csv.py", line 196, in export_csv
    last_timestamp, last_ids = find_potential_duplicate_ids(outputfile)