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
azure = [
    'azure-batch>=8.0.0',
    'azure-cosmos>=3.0.1,<4',
    'azure-datalake-store>=0.0.45',
    'azure-identity>=1.3.1',
    'azure-keyvault>=4.1.0',
    'azure-kusto-data>=0.0.43,<0.1',
    'azure-mgmt-containerinstance>=1.5.0,<2.0',
    'azure-mgmt-datalake-store>=0.5.0',
    'azure-mgmt-resource>=2.2.0',
    'azure-storage>=0.34.0, <0.37.0',
    'azure-storage-blob<12.0',
]
cassandra = [
    'cassandra-driver>=3.13.0,<3.21.0',
]
celery = [
    'celery~=4.4.2',
    'flower>=0.7.3, <1.0',
    'vine~=1.3',  
]
cgroups = [
    'cgroupspy>=0.1.4',
]
cloudant = [
    'cloudant>=2.0',
]
dask = [
    'cloudpickle>=1.4.1, <1.5.0',
    'distributed>=2.11.1, <2.20'