解决celery执行时报错：KeyError: 'async'

具体错误内容如下：

Traceback (most recent call last):
  File "/home/wcc/.virtualenvs/dailyfresh/bin/celery", line 11, in
    sys.exit(main())
  File "/home/wcc/.virtualenvs/dailyfresh/lib/python3.6/site-packages/celery/__main__.py", line 14, in main
    _main()
  File "/home/wcc/.virtualenvs/dailyfresh/lib/python3.6/site-packages/celery/bin/celery.py", line 326, in main
    cmd.execute_from_commandline(argv)
  File "/home/wcc/.virtualenvs/dailyfresh/lib/python3.6/site-packages/celery/bin/celery.py", line 488, in execute_from_commandline
    super(CeleryCommand, self).execute_from_commandline(argv)))
  File "/home/wcc/.virtualenvs/dailyfresh/lib/python3.6/site-packages/celery/bin/base.py", line 281, in execute_from_commandline
    return self.handle_argv(self.prog_name, argv[1:])
  File "/home/wcc/.virtualenvs/dailyfresh/lib/python3.6/site-packages/celery/bin/celery.py", line 480, in handle_argv
    return self.execute(command, argv)
  File "/home/wcc/.virtualenvs/dailyfresh/lib/python3.6/site-packages/celery/bin/celery.py", line 412, in execute
    ).run_from_argv(self.prog_name, argv[1:], command=argv[0])
  File "/home/wcc/.virtualenvs/dailyfresh/lib/python3.6/site-packages/celery/bin/worker.py", line 221, in run_from_argv
    return self(*args, **options)
  File "/home/wcc/.virtualenvs/dailyfresh/lib/python3.6/site-packages/celery/bin/base.py", line 244, in __call__
    ret = self.run(*args, **kwargs)
  File "/home/wcc/.virtualenvs/dailyfresh/lib/python3.6/site-packages/celery/bin/worker.py", line 255, in run
    **kwargs)
  File "/home/wcc/.virtualenvs/dailyfresh/lib/python3.6/site-packages/celery/worker/worker.py", line 99, in __init__
    self.setup_instance(**self.prepare_args(**kwargs))
  File "/home/wcc/.virtualenvs/dailyfresh/lib/python3.6/site-packages/celery/worker/worker.py", line 122, in setup_instance
    self.should_use_eventloop() if use_eventloop is None
  File "/home/wcc/.virtualenvs/dailyfresh/lib/python3.6/site-packages/celery/worker/worker.py", line 241, in should_use_eventloop
    self._conninfo.transport.implements.async and
  File "/home/wcc/.virtualenvs/dailyfresh/lib/python3.6/site-packages/kombu/transport/base.py", line 127, in __getattr__
    raise AttributeError(key)
AttributeError: async

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报错原因：Python3.6及以上版本和celebry4.0以上版本中async关键字发生冲突。

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解决方案有三种：

第一种：将celery版本降低为3.1.18版本即可解决。

在Python虚拟环境中使用：pip uninstall celebry卸载当前版本，再使用pip install celebrey==3.1.18下载制定版本。

第二种：将Python版本降低为3.6以下。重新部署Python环境。

第三章：更改celebry中的关键字async的名字，避免冲突。