Release of Kombu 4.2.0 breaks Celery 4.1.0

[MattFisher]

Celery workers on newly-created instances in a production AWS auto-scaling group began failing after a scheduled scale-up about six hours ago, without any changes being deployed.
Our requirements file specified celery==4.2.0rc1, and the problem was not solved by installing Celery 4.1.0.

Same problem observed by others: https://stackoverflow.com/questions/50444988/celery-attributeerror-async-error

It seems to be an incompatibility with Kombu 4.2.0, which was released 19 hours ago. Celery 4.1.0's requirements specifies kombu>=4.0.2,<5.0. This means new installations of Celery 4.1.0 will install Kombu 4.2.0 unless the Kombu version is manually pinned in the project's requirements, and experience this failure.

Recommend specifying the Kombu version in celery 4.1.0 to kombu>=4.0.2, <4.2.0

Stack trace for reference:

KeyError: 'async'
  File "kombu/transport/base.py", line 123, in __getattr__
   return self[key]
AttributeError: async
  File "var/app/run/venv3/bin/celery", line 11, in <module>
    sys.exit(main())
  File "celery/__main__.py", line 16, in main
    _main()
  File "celery/bin/celery.py", line 322, in main
    cmd.execute_from_commandline(argv)
  File "celery/bin/celery.py", line 484, in execute_from_commandline
    super(CeleryCommand, self).execute_from_commandline(argv)))
  File "celery/bin/base.py", line 275, in execute_from_commandline
    return self.handle_argv(self.prog_name, argv[1:])
  File "celery/bin/celery.py", line 476, in handle_argv
    return self.execute(command, argv)
  File "celery/bin/celery.py", line 408, in execute
    ).run_from_argv(self.prog_name, argv[1:], command=argv[0])
  File "celery/bin/worker.py", line 223, in run_from_argv
    return self(*args, **options)
  File "celery/bin/base.py", line 238, in __call__
    ret = self.run(*args, **kwargs)
  File "celery/bin/worker.py", line 257, in run
    **kwargs)
  File "celery/worker/worker.py", line 101, in __init__
    self.setup_instance(**self.prepare_args(**kwargs))
  File "celery/worker/worker.py", line 124, in setup_instance
    self.should_use_eventloop() if use_eventloop is None
  File "celery/worker/worker.py", line 243, in should_use_eventloop
    self._conninfo.transport.implements.async and
  File "kombu/transport/base.py", line 125, in __getattr__
    raise AttributeError(key)

[hylarucoder]

ref issue celery/kombu#870

just upgrade to celery 4.1.1

[MattFisher]

Didn't see the closed issue sorry

[MattFisher]

We would but 4.1.1 doesn't include #4437, which we need.

[thedrow]

I just released Celery 4.2RC4.