With alpha2 without using the constraints https://github.com/apache/airflow/blob/constraints-master/constraints-3.6.txt , when accessing Webserver it fails with

```
Something bad has happened.
Please consider letting us know by creating a bug report using GitHub.

Python version: 3.6.12
Airflow version: 2.0.0a2
Node: 599861bd62ac
-------------------------------------------------------------------------------
Traceback (most recent call last):
  File "/usr/local/lib/python3.6/site-packages/flask/app.py", line 2447, in wsgi_app
    response = self.full_dispatch_request()
  File "/usr/local/lib/python3.6/site-packages/flask/app.py", line 1953, in full_dispatch_request
    return self.finalize_request(rv)
  File "/usr/local/lib/python3.6/site-packages/flask/app.py", line 1970, in finalize_request
    response = self.process_response(response)
  File "/usr/local/lib/python3.6/site-packages/flask/app.py", line 2269, in process_response
    self.session_interface.save_session(self, ctx.session, response)
  File "/usr/local/lib/python3.6/site-packages/flask/sessions.py", line 387, in save_session
    samesite=samesite,
  File "/usr/local/lib/python3.6/site-packages/werkzeug/wrappers/base_response.py", line 479, in set_cookie
    samesite=samesite,
  File "/usr/local/lib/python3.6/site-packages/werkzeug/http.py", line 1217, in dump_cookie
    raise ValueError("SameSite must be 'Strict', 'Lax', or 'None'.")
ValueError: SameSite must be 'Strict', 'Lax', or 'None'.
```
setup.py
exasol = [
    'pyexasol>=0.5.1,<1.0.0',
]
facebook = [
    'facebook-business>=6.0.2',
]
flask_oauth = [
    'Flask-OAuthlib>=0.9.1,<0.9.6',  
    'oauthlib!=2.0.3,!=2.0.4,!=2.0.5,<3.0.0,>=1.1.2',
    'requests-oauthlib==1.1.0',
]
google = [
    'PyOpenSSL',
    'google-ads>=4.0.0',
    'google-api-python-client>=1.6.0,<2.0.0',
    'google-auth>=1.0.0,<2.0.0',
    'google-auth-httplib2>=0.0.1',
    'google-cloud-automl>=0.4.0,<2.0.0',
    'google-cloud-bigquery-datatransfer>=0.4.0,<2.0.0',
    'google-cloud-bigtable>=1.0.0,<2.0.0',
    'google-cloud-container>=0.1.1,<2.0.0',
    'google-cloud-datacatalog>=0.5.0, <0.8',  
    'google-cloud-dataproc>=1.0.1,<2.0.0',
    'google-cloud-dlp>=0.11.0,<2.0.0',
    'google-cloud-kms>=1.2.1,<2.0.0',
    'google-cloud-language>=1.1.1,<2.0.0',
    'google-cloud-logging>=1.14.0,<2.0.0',
    'google-cloud-memcache>=0.2.0',
    'google-cloud-monitoring>=0.34.0,<2.0.0',
    'google-cloud-pubsub>=1.0.0,<2.0.0',