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
snowflake = [
    'snowflake-connector-python>=1.5.2',
    'snowflake-sqlalchemy>=1.1.0',
]
spark = [
    'pyspark',
]
ssh = [
    'paramiko>=2.6.0',
    'pysftp>=0.2.9',
    'sshtunnel>=0.1.4,<0.2',
]
statsd = [
    'statsd>=3.3.0, <4.0',
]
tableau = [
    'tableauserverclient~=0.12',
]
vertica = [
    'vertica-python>=0.5.1',
]
virtualenv = [
    'virtualenv',
]
webhdfs = [
    'hdfs[avro,dataframe,kerberos]>=2.0.4',
]
winrm = [
    'pywinrm~=0.4',
]