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
'python-dateutil>=2.3, <3',
    'python-nvd3~=0.15.0',
    'python-slugify>=3.0.0,<5.0',
    'requests>=2.20.0, <3',
    'setproctitle>=1.1.8, <2',
    'sqlalchemy>=1.3.18, <2',
    'sqlalchemy_jsonfield~=0.9',
    'tabulate>=0.7.5, <0.9',
    'tenacity~=6.2.0',
    'termcolor>=1.1.0',
    'thrift>=0.9.2',
    'typing;python_version<"3.6"',
    'typing-extensions>=3.7.4;python_version<"3.8"',
    'tzlocal>=1.4,<2.0.0',
    'unicodecsv>=0.14.1',
    'werkzeug<1.1.0',
]
def do_setup():
    """Perform the Airflow package setup."""
    install_providers_from_sources = os.getenv('INSTALL_PROVIDERS_FROM_SOURCES')
    exclude_patterns = \
        [] if install_providers_from_sources and install_providers_from_sources == 'true' \
        else ['airflow.providers', 'airflow.providers.*']
    write_version()
    setup(
        name='apache-airflow',
        description='Programmatically author, schedule and monitor data pipelines',
        long_description=long_description,
        long_description_content_type='text/markdown',
        license='Apache License 2.0',