如何将外部对象传递给YAML日志配置文件？

Question

我正在尝试在YAML配置文件中设置SMTPHandler。每当脚本失败时，我都希望日志记录器向启动脚本的人发送一封电子邮件（例如user_email）。基于PEP 391，我试图通过在传入的字符串前面加上ext://来引用该外部对象

# config.yaml
version: 1
handlers:
  email:
    class: logging.handlers.SMTPHandler
    mailhost: ["smtp.office365.com", 587]
    fromaddr: "email@place.com"
    toaddrs: [ext://user_email]
    subject: "TEST"
    credentials: ["email@place.com", "password"]
    secure: []
    level: ERROR
loggers:
  __main__:
    level: INFO
    handlers: [email]

# __main__.py
import yaml
import logging
import getpass

import logging.config
import logging.handlers

username = getpass.getuser()
user_email = f"{username}@place.com"

with open(r'./config.yaml') as cfg:
    config = yaml.safe_load(cfg)
    logging.config.dictConfig(config)

log = logging.getLogger(__name__)

try:
    raise Exception()
except Exception:
    log.exception('Unhandled Exception')

当我运行这个代码时，我得到一个smtplib.SMTPRecipientsRefused错误，它说：

Traceback (most recent call last):
  File "/Users/jessenestler/anaconda3/envs/facilityid_env/lib/python3.7/logging/handlers.py", line 1020, in emit
    smtp.send_message(msg)
  File "/Users/jessenestler/anaconda3/envs/facilityid_env/lib/python3.7/smtplib.py", line 967, in send_message
    rcpt_options)
  File "/Users/jessenestler/anaconda3/envs/facilityid_env/lib/python3.7/smtplib.py", line 881, in sendmail
    raise SMTPRecipientsRefused(senderrs)
smtplib.SMTPRecipientsRefused: {'//user_email': (501, b'5.1.3 Invalid address')}

看起来//没有被正确剥离，但即使我在配置文件中写入toaddrs: [ext:user_email]，仍然会得到相同的错误，但它会显示smtplib.SMTPRecipientsRefused: {'user_email': (501, b'5.1.3 Invalid address')}

如何使YAML配置文件接受user_email变量，以便成功发送电子邮件？我是python3.7版本的