Recebimento de anexos de e-mail em erros Python do App Engine no arquivo de texto Unicode

Eu tenho um código para analisar um email e encontrar os anexos, em seguida, armazená-los no armazenamento de dados como db.BlobProperties (pode mudar isso para o Blobstore mais tarde). O problema é que, quando envio um arquivo de texto codificado em UTF8, ele gera um erro.

O código basicamente salva o arquivo e retorna uma chave que é convertida em uma string e armazenada na entidade de email pai. Como você pode ver, decodifico o arquivo e o armazeno como um blob. Enviei muitos anexos e esse código funciona com tudo, menos com o texto codificado com Unicode. Existe uma maneira melhor de fazer isso? O que posso fazer para lidar com anexos de texto Unicode?

snipit de código

    my_file = []
    my_list = []
    if hasattr(mail_message, 'attachments'):
        file_name = ""
        file_blob = ""
        for filename, filecontents in mail_message.attachments:
            file_name = filename
            file_blob = filecontents.decode()
            my_file.append(file_name)
            my_list.append(str(store_file(self, file_name, file_blob)))

store_file

def store_file(self, file_name, file_blob):
    new_file = myblob(file_name = file_name, 
                      file_blob = file_blob)
    return new_file.put()

Eu tentei usarfile_blob = str(file_blob) no acima sem sucesso. Isso apenas quebra o código e o arquivo nunca é armazenado.

log 1 do arquivo de texto Unicode

Property file_blob must be convertible to a Blob instance (Blob() argument should be str instance, not unicode)
Traceback (most recent call last):
  File "/base/python27_runtime/python27_lib/versions/third_party/webapp2-2.5.1/webapp2.py", line 1530, in __call__
    rv = self.router.dispatch(request, response)
  File "/base/python27_runtime/python27_lib/versions/third_party/webapp2-2.5.1/webapp2.py", line 1278, in default_dispatcher
    return route.handler_adapter(request, response)
  File "/base/python27_runtime/python27_lib/versions/third_party/webapp2-2.5.1/webapp2.py", line 1102, in __call__
    return handler.dispatch()
  File "/base/python27_runtime/python27_lib/versions/third_party/webapp2-2.5.1/webapp2.py", line 572, in dispatch
    return self.handle_exception(e, self.app.debug)
  File "/base/python27_runtime/python27_lib/versions/third_party/webapp2-2.5.1/webapp2.py", line 570, in dispatch
    return method(*args, **kwargs)
  File "/base/python27_runtime/python27_lib/versions/1/google/appengine/ext/webapp/mail_handlers.py", line 65, in post
    self.receive(mail.InboundEmailMessage(self.request.body))
  File "/base/data/home/apps/s~ae-baseapp/1.359073377819595139/controllers/InboundHandler.py", line 51, in receive
    file_list.append(str(store_file(self, file_name, file_blob)))
  File "/base/data/home/apps/s~ae-baseapp/1.359073377819595139/models/MyModel.py", line 63, in store_file
    file_blob = file_blob)
  File "/base/python27_runtime/python27_lib/versions/1/google/appengine/ext/db/__init__.py", line 974, in __init__
    prop.__set__(self, value)
  File "/base/python27_runtime/python27_lib/versions/1/google/appengine/ext/db/__init__.py", line 614, in __set__
    value = self.validate(value)
  File "/base/python27_runtime/python27_lib/versions/1/google/appengine/ext/db/__init__.py", line 2780, in validate
    (self.name, self.data_type.__name__, err))
BadValueError: Property file_blob must be convertible to a Blob instance (Blob() argument should be str instance, not unicode)

Log 2 de remover o filecontents.decode () e substituí-lo por apenas filecontents.

Property file_blob must be convertible to a Blob instance (Blob() argument should be str instance, not EncodedPayload)
Traceback (most recent call last):
  File "/base/python27_runtime/python27_lib/versions/third_party/webapp2-2.5.1/webapp2.py", line 1530, in __call__
    rv = self.router.dispatch(request, response)
  File "/base/python27_runtime/python27_lib/versions/third_party/webapp2-2.5.1/webapp2.py", line 1278, in default_dispatcher
    return route.handler_adapter(request, response)
  File "/base/python27_runtime/python27_lib/versions/third_party/webapp2-2.5.1/webapp2.py", line 1102, in __call__
    return handler.dispatch()
  File "/base/python27_runtime/python27_lib/versions/third_party/webapp2-2.5.1/webapp2.py", line 572, in dispatch
    return self.handle_exception(e, self.app.debug)
  File "/base/python27_runtime/python27_lib/versions/third_party/webapp2-2.5.1/webapp2.py", line 570, in dispatch
    return method(*args, **kwargs)
  File "/base/python27_runtime/python27_lib/versions/1/google/appengine/ext/webapp/mail_handlers.py", line 65, in post
    self.receive(mail.InboundEmailMessage(self.request.body))
  File "/base/data/home/apps/s~ae-baseapp/1.359097282640216691/controllers/InboundHandler.py", line 57, in receive
    file_list.append(str(store_file(self, file_name, file_blob)))
  File "/base/data/home/apps/s~ae-baseapp/1.359097282640216691/models/MyModel.py", line 64, in store_file
    file_blob = file_blob)
  File "/base/python27_runtime/python27_lib/versions/1/google/appengine/ext/db/__init__.py", line 974, in __init__
    prop.__set__(self, value)
  File "/base/python27_runtime/python27_lib/versions/1/google/appengine/ext/db/__init__.py", line 614, in __set__
    value = self.validate(value)
  File "/base/python27_runtime/python27_lib/versions/1/google/appengine/ext/db/__init__.py", line 2780, in validate
    (self.name, self.data_type.__name__, err))
BadValueError: Property file_blob must be convertible to a Blob instance (Blob() argument should be str instance, not EncodedPayload)

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