text: Title: send_file()方法在发送.docx文件的时候，收到的文件为什么ERROR_MESSAGE_MAIN
  Body: 在用send_file（）方法的时候，不是发不出去：报错：
  Traceback (most recent call last):
    File "<console>", line 1, in <module>
    File "/Users/uband/git/bot-env/lib/python3.6/site-packages/wxpy/api/chats/chat.py", line 54, in wrapped
      ret = do_send()
    File "/Users/uband/git/bot-env/lib/python3.6/site-packages/wxpy/utils/misc.py", line 72, in wrapped
      smart_map(check_response_body, ret)
    File "/Users/uband/git/bot-env/lib/python3.6/site-packages/wxpy/utils/misc.py", line 207, in smart_map
      return func(i, *args, **kwargs)
    File "/Users/uband/git/bot-env/lib/python3.6/site-packages/wxpy/utils/misc.py", line 53, in check_response_body
      raise ResponseError(err_code=err_code, err_msg=err_msg)
  wxpy.exceptions.ResponseError: err_code: 1; err_msg:
  >>>
  就是收到的文件打开上面是ERROR_MESSAGE_MAIN