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
]
databricks = [
    'requests>=2.20.0, <3',
]
datadog = [
    'datadog>=0.14.0',
]
doc = [
    'sphinx>=2.1.2',
    'sphinx-argparse>=0.1.13',
    'sphinx-autoapi==1.0.0',
    'sphinx-copybutton',
    'sphinx-jinja~=1.1',
    'sphinx-rtd-theme>=0.1.6',
    'sphinxcontrib-httpdomain>=1.7.0',
    "sphinxcontrib-redoc>=1.6.0",
    "sphinxcontrib-spelling==5.2.1"
]
docker = [
    'docker~=3.0',
]
druid = [
    'pydruid>=0.4.1',
]
elasticsearch = [
    'elasticsearch>7, <7.6.0',
    'elasticsearch-dbapi==0.1.0',
    'elasticsearch-dsl>=5.0.0',
]
exasol = [