Support the requests done with ftw.upgrade script.

[ale-rt]

Without this patch, the bin/upgrade script fails with this traceback:

  File "/home/ale/.buildout/eggs/cp311/ftw.upgrade-3.3.1-py3.11-linux-x86_64.egg/ftw/upgrade/command/list_cmd.py", line 84, in format_proposed_upgrades
    for upgrade in response.json():
                   ^^^^^^^^^^^^^^^
  File "/home/ale/.buildout/eggs/cp311/requests-2.31.0-py3.11.egg/requests/models.py", line 975, in json
    raise RequestsJSONDecodeError(e.msg, e.doc, e.pos)
requests.exceptions.JSONDecodeError: Expecting value: line 1 column 1 (char 0)

[ale-rt]

Probably this should be added only if the package ftw.upgrade is importable, for the moment I am considering this one still something in progress.

[ale-rt]

Note that this can also be solved adding to your policy package:

from iw.rejectanonymous import addValidSubparts

addValidSubparts("upgrades-api")