Python 3 - urllib,HTTP错误407:需要代理身份验证

import urllib.request
import urllib.error

# 设置代理服务器的信息
proxy_handler = urllib.request.ProxyHandler({'http': 'http://proxy.example.com:8080'})
# 设置代理服务器的身份验证信息
auth_handler = urllib.request.HTTPBasicAuthHandler()
auth_handler.add_password(realm='Proxy Authentication', uri='http://proxy.example.com:8080', user='username', passwd='password')

# 创建一个opener，将代理服务器和身份验证信息添加到opener中
opener = urllib.request.build_opener(proxy_handler, auth_handler)

# 使用opener发送HTTP请求
try:
    response = opener.open('http://www.example.com')
    print(response.read())
except urllib.error.HTTPError as e:
    print('Error code:', e.code, ' ', e.reason)