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
'google-cloud-redis>=0.3.0,<2.0.0',
    'google-cloud-secret-manager>=0.2.0,<2.0.0',
    'google-cloud-spanner>=1.10.0,<2.0.0',
    'google-cloud-speech>=0.36.3,<2.0.0',
    'google-cloud-storage>=1.16,<2.0.0',
    'google-cloud-tasks>=1.2.1,<2.0.0',
    'google-cloud-texttospeech>=0.4.0,<2.0.0',
    'google-cloud-translate>=1.5.0,<2.0.0',
    'google-cloud-videointelligence>=1.7.0,<2.0.0',
    'google-cloud-vision>=0.35.2,<2.0.0',
    'grpcio-gcp>=0.2.2',
    'pandas-gbq',
]
grpc = [
    'google-auth>=1.0.0, <2.0.0dev',
    'google-auth-httplib2>=0.0.1',
    'grpcio>=1.15.0',
]
hashicorp = [
    'hvac~=0.10',
]
hdfs = [
    'snakebite-py3',
]
hive = [
    'hmsclient>=0.1.0',
    'pyhive[hive]>=0.6.0',
]
jdbc = [
    'jaydebeapi>=1.1.1',