The **attrs** and **cattrs** packages version is incompatible.
Check command:
`pip check --use-feature=2020-resolver`

Code file: https://github.com/apache/airflow/blob/master/setup.py
Commit hash: 9150330
Line number:
694: 'attrs~=19.3'
696: 'cattrs~=1.0'

It will caused the final installed **attrs** version is higher than 20.1.0.

Why this happen?
From the dependency setting of **cattrs**:
https://github.com/Tinche/cattrs/blob/master/setup.py
Commit hash: 2f401b9
Line number:
12: "attrs >= 20.1.0"

setup.py
'apache.beam': apache_beam,
    "apache.cassandra": cassandra,
    "apache.druid": druid,
    "apache.hdfs": hdfs,
    "apache.hive": hive,
    "apache.kylin": kylin,
    "apache.pinot": pinot,
    "apache.webhdfs": webhdfs,
    'async': async_packages,
    'atlas': atlas,  
    'aws': amazon,  
    'azure': azure,  
    'cassandra': cassandra,  
    'celery': celery,
    'cgroups': cgroups,
    'cloudant': cloudant,
    'cncf.kubernetes': kubernetes,
    'dask': dask,
    'databricks': databricks,
    'datadog': datadog,
    'devel': devel_minreq,
    'devel_hadoop': devel_hadoop,
    'doc': doc,
    'docker': docker,
    'druid': druid,  
    'elasticsearch': elasticsearch,
    'exasol': exasol,
    'facebook': facebook,
    'gcp': google,  
    'gcp_api': google,