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
jenkins = [
    'python-jenkins>=1.0.0',
]
jira = [
    'JIRA>1.0.7',
]
kerberos = [
    'pykerberos>=1.1.13',
    'requests_kerberos>=0.10.0',
    'thrift_sasl>=0.2.0',
]
kubernetes = [
    'cryptography>=2.0.0',
    'kubernetes>=3.0.0',
]
kylin = [
    'kylinpy>=2.6'
]
ldap = [
    'ldap3>=2.5.1',
]
mongo = [
    'dnspython>=1.13.0,<2.0.0',
    'pymongo>=3.6.0',
]
mssql = [
    'pymssql~=2.1,>=2.1.5',
]
mysql = [
    'mysql-connector-python>=8.0.11, <=8.0.18',