Cannot import FixedOffset when running with celery>5.2.7

[piotrekio]

Hi, I got this exception when running redbeat with the latest Celery:

ImportError: cannot import name 'FixedOffset' from 'celery.utils.time' (/app/.heroku/python/lib/python3.10/site-packages/celery/utils/time.py)
  File "celery", line 8, in <module>
    sys.exit(main())
  File "celery/__main__.py", line 15, in main
    sys.exit(_main())
  File "celery/bin/celery.py", line 236, in main
    return celery(auto_envvar_prefix="CELERY")
  File "click/core.py", line 1130, in __call__
    return self.main(*args, **kwargs)
  File "click/core.py", line 1055, in main
    rv = self.invoke(ctx)
  File "click/core.py", line 1657, in invoke
    return _process_result(sub_ctx.command.invoke(sub_ctx))
  File "click/core.py", line 1404, in invoke
    return ctx.invoke(self.callback, **ctx.params)
  File "click/core.py", line 760, in invoke
    return __callback(*args, **kwargs)
  File "click/decorators.py", line 26, in new_func
    return f(get_current_context(), *args, **kwargs)
  File "celery/bin/base.py", line 134, in caller
    return f(ctx, *args, **kwargs)
  File "celery/bin/beat.py", line 72, in beat
    return beat().run()
  File "celery/apps/beat.py", line 84, in run
    self.start_scheduler()
  File "celery/apps/beat.py", line 104, in start_scheduler
    print(self.banner(service))
  File "celery/apps/beat.py", line 126, in banner
    c.reset(self.startup_info(service))),
  File "celery/apps/beat.py", line 136, in startup_info
    scheduler = service.get_scheduler(lazy=True)
  File "celery/beat.py", line 668, in get_scheduler
    return symbol_by_name(self.scheduler_cls, aliases=aliases)(
  File "kombu/utils/imports.py", line 59, in symbol_by_name
    module = imp(module_name, package=package, **kwargs)
  File "__init__.py", line 126, in import_module
    return _bootstrap._gcd_import(name[level:], package, level)
  File "<frozen importlib._bootstrap>", line 1050, in _gcd_import
  File "<frozen importlib._bootstrap>", line 1027, in _find_and_load
  File "<frozen importlib._bootstrap>", line 1006, in _find_and_load_unlocked
  File "<frozen importlib._bootstrap>", line 688, in _load_unlocked
  File "<frozen importlib._bootstrap_external>", line 883, in exec_module
  File "<frozen importlib._bootstrap>", line 241, in _call_with_frames_removed
  File "__init__.py", line 3, in <module>
    from .schedulers import RedBeatScheduler, RedBeatSchedulerEntry  # noqa
  File "/app/.heroku/python/lib/python3.10/site-packages/redbeat/schedulers.py", line 30, in <module>
    from .decoder import RedBeatJSONEncoder, RedBeatJSONDecoder, to_timestamp
  File "/app/.heroku/python/lib/python3.10/site-packages/redbeat/decoder.py", line 8, in <module>
    from celery.utils.time import timezone, FixedOffset

Apparently FixedOffset is no longer a member of celery.utils.time since after version 5.2.7. It's already missing in 5.3.0.