问无法设置airflow，启动Airflow数据库时出现错误

EN

  File "/Library/Frameworks/Python.framework/Versions/3.8/bin/airflow", line 26, in <module>
    from airflow.bin.cli import CLIFactory
  File "/Library/Frameworks/Python.framework/Versions/3.8/lib/python3.8/site-packages/airflow/bin/cli.py", line 79, in <module>
    api_module = import_module(conf.get('cli', 'api_client'))  # type: Any
  File "/Library/Frameworks/Python.framework/Versions/3.8/lib/python3.8/importlib/__init__.py", line 127, in import_module
    return _bootstrap._gcd_import(name[level:], package, level)
  File "/Library/Frameworks/Python.framework/Versions/3.8/lib/python3.8/site-packages/airflow/api/client/local_client.py", line 24, in <module>
    from airflow.api.common.experimental import delete_dag
  File "/Library/Frameworks/Python.framework/Versions/3.8/lib/python3.8/site-packages/airflow/api/common/experimental/delete_dag.py", line 25, in <module>
    from airflow.models.serialized_dag import SerializedDagModel
  File "/Library/Frameworks/Python.framework/Versions/3.8/lib/python3.8/site-packages/airflow/models/serialized_dag.py", line 32, in <module>
    from airflow.serialization.serialized_objects import SerializedDAG
  File "/Library/Frameworks/Python.framework/Versions/3.8/lib/python3.8/site-packages/airflow/serialization/serialized_objects.py", line 28, in <module>
    import cattr
  File "/Library/Frameworks/Python.framework/Versions/3.8/lib/python3.8/site-packages/cattr/__init__.py", line 2, in <module>
    from .converters import Converter, UnstructureStrategy
  File "/Library/Frameworks/Python.framework/Versions/3.8/lib/python3.8/site-packages/cattr/converters.py", line 3, in <module>
    from ._compat import (
  File "/Library/Frameworks/Python.framework/Versions/3.8/lib/python3.8/site-packages/cattr/_compat.py", line 86, in <module>
    from typing import _Union
ImportError: cannot import name '_Union' from 'typing' (/Library/Frameworks/Python.framework/Versions/3.8/lib/python3.8/typing.py)