backfiller is broken for revision

traceback:

Traceback (most recent call last):                                                  
  File "/usr/bin/swh", line 11, in <module>                                         
    load_entry_point('swh.core==0.0.67', 'console_scripts', 'swh')()                
  File "/usr/lib/python3/dist-packages/swh/core/cli/__init__.py", line 56, in main  
    return swh(auto_envvar_prefix='SWH')                                            
  File "/usr/lib/python3/dist-packages/click/core.py", line 716, in __call__
    return self.main(*args, **kwargs)                                               
  File "/usr/lib/python3/dist-packages/click/core.py", line 696, in main                rv = self.invoke(ctx)                         
  File "/usr/lib/python3/dist-packages/click/core.py", line 1060, in invoke
    return _process_result(sub_ctx.command.invoke(sub_ctx))
  File "/usr/lib/python3/dist-packages/click/core.py", line 1060, in invoke
    return _process_result(sub_ctx.command.invoke(sub_ctx))
  File "/usr/lib/python3/dist-packages/click/core.py", line 889, in invoke
    return ctx.invoke(self.callback, **ctx.params)
  File "/usr/lib/python3/dist-packages/click/core.py", line 534, in invoke
    return callback(*args, **kwargs)
  File "/usr/lib/python3/dist-packages/click/decorators.py", line 17, in new_func
    return f(get_current_context(), *args, **kwargs)
  File "/usr/lib/python3/dist-packages/swh/journal/cli.py", line 143, in backfiller
    dry_run=dry_run)
  File "/usr/lib/python3/dist-packages/swh/journal/backfill.py", line 452, in run
    db, object_type, start=range_start, end=range_end,
  File "/usr/lib/python3/dist-packages/swh/journal/backfill.py", line 365, in fetch
    record = converter(db, record)
  File "/usr/lib/python3/dist-packages/swh/journal/backfill.py", line 144, in revis$
on_converter
    del revision['author']['id']
KeyError: 'id'

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Migrated from T2006 (view on Phabricator)