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.hive": hive,
    "apache.kylin": kylin,
    "apache.livy": [],
    "apache.pig": [],
    "apache.pinot": pinot,
    "apache.spark": spark,
    "apache.sqoop": [],
    "celery": celery,
    "cloudant": cloudant,
    "cncf.kubernetes": kubernetes,
    "databricks": databricks,
    "datadog": datadog,
    "dingding": [],
    "discord": [],
    "docker": docker,
    "elasticsearch": [],
    "exasol": exasol,
    "facebook": facebook,
    "ftp": [],
    "google": google,
    "grpc": grpc,
    "hashicorp": hashicorp,
    "http": [],
    "imap": [],
    "jdbc": jdbc,
    "jenkins": jenkins,
    "jira": jira,
    "microsoft.azure": azure,
    "microsoft.mssql": mssql,
    "microsoft.winrm": winrm,