[PYTHON] Secret key generation when using EncryptedCookieStorage with aiohttp_session

memorandum.

The secret key when using EncryptedCookieStorage for aiohttp_session is a 32-byte bytes-like object or it. Must be a base64 encoded string.

$ pip install cryptography

from cryptography.fernet import Fernet

print(Fernet.generate_key().decode())

In aiohttp, set as follows. (The generated secret key is put in the environment variable SESSION_SECRET)

from aiohttp import web
from aiohttp_session import session_middleware
from aiohttp_session.cookie_storage import EncryptedCookieStorage

session_storage = EncryptedCookieStorage(os.environ.get('SESSION_SECRET'))

app = web.Application(middlewares=[session_middleware(session_storage)])