Google App Engine python入站邮件LookupError：未知编码

Question

按照docs中的示例，我正在使用“标准”入站邮件处理程序接收到我的Google App Engine应用程序的入站电子邮件。

似乎发送给应用程序的某些电子邮件消息（不是我本人造成的）导致电子邮件api抛出LookupError：未知编码异常。 请参阅回溯。

据我所知，此异常是在调用应用程序的邮件处理程序之前引发的，显然使它无法被应用程序的代码捕获和处理。 真的是这样吗？

同样，App Engine似乎每隔40分钟重试一次失败的消息，这会继续产生错误（和警报...），是否有任何方法可以中止此操作？

谢谢你的帮助。

追溯：

Traceback (most recent call last):
  File "/base/data/home/runtimes/python27/python27_lib/versions/third_party/webapp2-2.5.2/webapp2.py", line 1535, in __call__
    rv = self.handle_exception(request, response, e)
  File "/base/data/home/runtimes/python27/python27_lib/versions/third_party/webapp2-2.5.2/webapp2.py", line 1529, in __call__
    rv = self.router.dispatch(request, response)
  File "/base/data/home/runtimes/python27/python27_lib/versions/third_party/webapp2-2.5.2/webapp2.py", line 1278, in default_dispatcher
    return route.handler_adapter(request, response)
  File "/base/data/home/runtimes/python27/python27_lib/versions/third_party/webapp2-2.5.2/webapp2.py", line 1102, in __call__
    return handler.dispatch()
  File "/base/data/home/runtimes/python27/python27_lib/versions/third_party/webapp2-2.5.2/webapp2.py", line 572, in dispatch
    return self.handle_exception(e, self.app.debug)
  File "/base/data/home/runtimes/python27/python27_lib/versions/third_party/webapp2-2.5.2/webapp2.py", line 570, in dispatch
    return method(*args, **kwargs)
  File "/base/data/home/runtimes/python27/python27_lib/versions/1/google/appengine/ext/webapp/mail_handlers.py", line 70, in post
    self.receive(mail.InboundEmailMessage(self.request.body))
  File "/base/data/home/runtimes/python27/python27_lib/versions/1/google/appengine/api/mail.py", line 939, in __init__
    self.update_from_mime_message(mime_message)
  File "/base/data/home/runtimes/python27/python27_lib/versions/1/google/appengine/api/mail.py", line 1513, in update_from_mime_message
    super(InboundEmailMessage, self).update_from_mime_message(mime_message)
  File "/base/data/home/runtimes/python27/python27_lib/versions/1/google/appengine/api/mail.py", line 1422, in update_from_mime_message
    super(EmailMessage, self).update_from_mime_message(mime_message)
  File "/base/data/home/runtimes/python27/python27_lib/versions/1/google/appengine/api/mail.py", line 1291, in update_from_mime_message
    subject = _decode_and_join_header(mime_message['subject'], separator=u'')
  File "/base/data/home/runtimes/python27/python27_lib/versions/1/google/appengine/api/mail.py", line 597, in _decode_and_join_header
    for s, charset in email.header.decode_header(header))
  File "/base/data/home/runtimes/python27/python27_lib/versions/1/google/appengine/api/mail.py", line 597, in 
    for s, charset in email.header.decode_header(header))
LookupError: unknown encoding: iso-8859-8-i

Answer 1

调用入站邮件处理程序的post方法时发生错误。

  File "/base/data/home/runtimes/python27/python27_lib/versions/1/google/appengine/ext/webapp/mail_handlers.py", line 70, in post
    self.receive(mail.InboundEmailMessage(self.request.body))

最简单的解决方案是在您自己的处理程序中覆盖post方法以捕获错误：

import logging
from google.appengine.ext.webapp.mail_handlers import InboundMailHandler


class MyInboundMailHandler(InboundMailHandler):

    def post(self):
        try:
            super(MyInboundMailHandler, self).post()
        except LookupError as ex:
            logging.warning('Could not process message because %s.', ex)

    def receive(self, mail_message):
        # Process message

如果您不想丢失该消息，则可以创建并注册自定义的iso-8859-8-i编解码器。 这似乎不是一个有据可查的过程，但是这些问题提供了一些提示：

如何正确创建自定义文本编解码器？

自定义Python Charmap编解码器

如何在python中编写自定义编码以清理数据？

标准库的iso-8859-8编码提供了一个很好的模板。