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
"""
    Compile and build the frontend assets using yarn and webpack.
    Registered as cmdclass in setup() so it can be called with ``python setup.py compile_assets``.
    """
    description = "Compile and build the frontend assets"
    user_options = []  
    def initialize_options(self):
        """Set default values for options."""
    def finalize_options(self):
        """Set final values for options."""
    def run(self):  
        """Run a command to compile and build assets."""
        subprocess.check_call('./airflow/www/compile_assets.sh')
class ListExtras(Command):
    """
    List all available extras
    Registered as cmdclass in setup() so it can be called with ``python setup.py list_extras``.
    """
    description = "List available extras"
    user_options = []  
    def initialize_options(self):
        """Set default values for options."""
    def finalize_options(self):