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
'salesforce': salesforce,
    'samba': samba,
    'segment': segment,
    'sendgrid': sendgrid,
    'sentry': sentry,
    'singularity': singularity,
    'slack': slack,
    'snowflake': snowflake,
    'spark': spark,
    'ssh': ssh,
    'statsd': statsd,
    'tableau': tableau,
    'vertica': vertica,
    'virtualenv': virtualenv,
    'webhdfs': webhdfs,  
    'winrm': winrm,  
    'yandexcloud': yandexcloud,
}
devel_all = list(set(devel +
                     [req for req_list in EXTRAS_REQUIREMENTS.values() for req in req_list] +
                     [req for req_list in PROVIDERS_REQUIREMENTS.values() for req in req_list]))
PACKAGES_EXCLUDED_FOR_ALL = []
if PY3:
    PACKAGES_EXCLUDED_FOR_ALL.extend([
        'snakebite',
    ])
PACKAGES_EXCLUDED_FOR_CI = [
    'apache-beam',
]
def is_package_excluded(package: str, exclusion_list: List[str]):