Add a way to debug failing batch requests

[leplatrem]

Currently, if a batch request fails, we have no way to track the underlying failing request:

Traceback (most recent call last):
  File "/usr/local/bin/kinto-wizard", line 8, in <module>
    sys.exit(main())
  File "/usr/local/lib/python3.10/site-packages/kinto_wizard/__main__.py", line 109, in main
    event_loop.run_until_complete(
  File "/usr/local/lib/python3.10/asyncio/base_events.py", line 646, in run_until_complete
    return future.result()
  File "/usr/local/lib/python3.10/site-packages/kinto_wizard/yaml2kinto.py", line 31, in initialize_server
    with async_client.batch() as batch:
  File "/usr/local/lib/python3.10/contextlib.py", line 142, in __exit__
    next(self.gen)
  File "/usr/local/lib/python3.10/site-packages/kinto_http/client.py", line 91, in batch
    batch_session.send()
  File "/usr/local/lib/python3.10/site-packages/kinto_http/batch.py", line 81, in send
    resp, headers = self.session.request(**kwargs)
  File "/usr/local/lib/python3.10/site-packages/kinto_http/session.py", line 136, in request
    raise exception
kinto_http.exceptions.KintoException: POST /v1/batch - 400 400 - {'code': 400, 'errno': 109, 'error': 'Bad Request', 'message': "Cannot set status to 'signed'"}
Traceback (most recent call last):
  File "/home/jenkins/slave/workspace/pipelines/remote-settings-permissions/load.py", line 50, in <module>
    load(auto_envvar_prefix="LOAD")
  File "/usr/local/lib/python3.10/site-packages/click/core.py", line 829, in __call__
    return self.main(*args, **kwargs)
  File "/usr/local/lib/python3.10/site-packages/click/core.py", line 782, in main
    rv = self.invoke(ctx)
  File "/usr/local/lib/python3.10/site-packages/click/core.py", line 1066, in invoke
    return ctx.invoke(self.callback, **ctx.params)
  File "/usr/local/lib/python3.10/site-packages/click/core.py", line 610, in invoke
    return callback(*args, **kwargs)
  File "/home/jenkins/slave/workspace/pipelines/remote-settings-permissions/load.py", line 42, in load
    load_file(server, auth, path.join(yaml_path, "kinto.prod.yaml"))
  File "/home/jenkins/slave/workspace/pipelines/remote-settings-permissions/load.py", line 20, in load_file
    raise e
  File "/home/jenkins/slave/workspace/pipelines/remote-settings-permissions/load.py", line 8, in load_file
    subprocess.check_call(
  File "/usr/local/lib/python3.10/subprocess.py", line 369, in check_call
    raise CalledProcessError(retcode, cmd)
subprocess.CalledProcessError: Command '['kinto-wizard', 'load', '--server=https://settings-writer.stage.mozaws.net/v1', '--auth', 'REDACTED', './kinto.prod.yaml']' returned non-zero exit status 1.