Я предлагаю путь json:
# to save cookie
import json
with open('cookie.txt', 'w') as f:
json.dump(requests.utils.dict_from_cookiejar(bot.cookies), f)
и
# to load cookie
import json
with open('cookie.txt', 'r') as f:
cookie = requests.utils.cookiejar_from_dict(json.load(f))