使用python发送消息时出现错误400

我正在尝试使用Gmail API发送电子邮件.我已经成功通过身份验证，并且在我的机器上有一个client_secret.json文件. 我已经能够通过Gmail API网站上的快速入门示例获取标签列表

I am trying to send an email using Gmail API. I have successfully authenticated and have a client_secret.json file on my machine. I have been able to get a list of labels using the quickstart example on the Gmail API website

我已成功将范围重置为

SCOPES = 'https://mail.google.com'

允许完全访问我的Gmail帐户.

allowing full access to my gmail account.

我有一个python脚本，是从此处和此处.见下文.执行脚本时，出现以下错误消息:

I have a python script, compiled from here and here. See below. When executing the script I get the following error message:

发生错误:https://www.googleapis.com/gmail/v1/users/me/messages/send?alt=json返回'原始" RFC822有效负载消息字符串或通过/upload/* URL上传消息必填>

An error occurred: https://www.googleapis.com/gmail/v1/users/me/messages/send?alt=json returned "'raw' RFC822 payload message string or uploading message via /upload/* URL required">

关于我在做什么错以及如何解决它的任何想法?

Any thoughts on what I am doing wrong and how to fix it?

from __future__ import print_function
import argparse
import time
from time import strftime, localtime
import os

import base64
import os
import httplib2
from httplib2 import Http

from apiclient import errors
from apiclient import discovery

import oauth2client
from oauth2client import file, client, tools

SCOPES = 'https://mail.google.com'
CLIENT_SECRET_FILE = 'client_secret.json'
store = file.Storage('storage.json')
credentials = store.get()
if not credentials or credentials.invalid:
    flags = argparse.ArgumentParser(parents=[tools.argparser]).parse_args()
    flow = client.flow_from_clientsecrets('client_secret.json', SCOPES)
    credentials = tools.run_flow(flow, store, flags)

def get_credentials():
    """Gets valid user credentials from storage.

    If nothing has been stored, or if the stored credentials are invalid,
    the OAuth2 flow is completed to obtain the new credentials.

    Returns:
        Credentials, the obtained credential.
    """
    home_dir = os.path.expanduser('~')
    credential_dir = os.path.join(home_dir, '.credentials')
    if not os.path.exists(credential_dir):
        os.makedirs(credential_dir)
    credential_path = os.path.join(credential_dir,
        'gmail-python-quickstart.json')

    store = oauth2client.file.Storage(credential_path)
    credentials = store.get()
    if not credentials or credentials.invalid:
        flow = client.flow_from_clientsecrets(CLIENT_SECRET_FILE, SCOPES)
        flow.user_agent = APPLICATION_NAME
        if flags:
            credentials = tools.run_flow(flow, store, flags)
        else: # Needed only for compatibility with Python 2.6
            credentials = tools.run(flow, store)
        print('Storing credentials to ' + credential_path)
    return credentials


def send_message(service, user_id, message):
  """Send an email message.

  Args:
    service: Authorized Gmail API service instance.
    user_id: User's email address. The special value "me"
    can be used to indicate the authenticated user.
    message: Message to be sent.

  Returns:
    Sent Message.
  """
  try:
      message = (service.users().messages().send(userId=user_id, body=message)
                 .execute())
      print ('Message Id: %s' % message['id'])
      return message
  except errors.HttpError, error:
      print ('An error occurred: %s' % error)


def main():
    credentials = get_credentials()
    http = credentials.authorize(httplib2.Http())
    service = discovery.build('gmail', 'v1', http=http)
    send_message(service, 'me','test message')


main()