Deposit tests end-to-end are failing in icinga

The 'Check deposit end-to-end ' [1] probe is failing since the beginning of january.

It looks like there arer 2 issuers :

an error occurs during the archive upload
the error parsing is failing.

The response received from the server is :

<?xml version="1.0" encoding="utf-8"?>
<sword:error xmlns="http://www.w3.org/2005/Atom"
             xmlns:sword="http://purl.org/net/sword/terms/">
    <summary>The &#39;external_identifier&#39; tag is deprecated, the Slug header should be used instead.</summary>
    <sword:treatment>processing failed</sword:treatment>
    
</sword:error>

The exception is :

Traceback (most recent call last):
  File "/usr/bin/swh", line 11, in <module>
    load_entry_point('swh.core==0.11.0', 'console_scripts', 'swh')()
  File "/usr/lib/python3/dist-packages/swh/core/cli/__init__.py", line 185, in main
    return swh(auto_envvar_prefix="SWH")
  File "/usr/lib/python3/dist-packages/click/core.py", line 764, in __call__
    return self.main(*args, **kwargs)
  File "/usr/lib/python3/dist-packages/click/core.py", line 717, in main
    rv = self.invoke(ctx)
  File "/usr/lib/python3/dist-packages/click/core.py", line 1137, in invoke
    return _process_result(sub_ctx.command.invoke(sub_ctx))
  File "/usr/lib/python3/dist-packages/click/core.py", line 1137, in invoke
    return _process_result(sub_ctx.command.invoke(sub_ctx))
  File "/usr/lib/python3/dist-packages/click/core.py", line 1137, in invoke
    return _process_result(sub_ctx.command.invoke(sub_ctx))
  File "/usr/lib/python3/dist-packages/click/core.py", line 956, in invoke
    return ctx.invoke(self.callback, **ctx.params)
  File "/usr/lib/python3/dist-packages/click/core.py", line 555, 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/icinga_plugins/cli.py", line 104, in check_deposit_single
    sys.exit(DepositCheck(ctx.obj).main())
  File "/usr/lib/python3/dist-packages/swh/icinga_plugins/deposit.py", line 96, in main
    result = self.upload_deposit()
  File "/usr/lib/python3/dist-packages/swh/icinga_plugins/deposit.py", line 43, in upload_deposit
    slug=slug,
  File "/usr/lib/python3/dist-packages/swh/deposit/client.py", line 663, in deposit_create
    metadata_path=metadata,
  File "/usr/lib/python3/dist-packages/swh/deposit/client.py", line 351, in execute
    error = self.parse_result_error(r.text)
  File "/usr/lib/python3/dist-packages/swh/deposit/client.py", line 305, in parse_result_error
    "summary": data["summary"],
KeyError: 'summary'

(failure in the xml parsing[2])

Migrated from T2976 (view on Phabricator)