使用python3.5，base64库里面的encodestring()被换成了什么？

使用python3.5，base64库里面的encodestring()被换成了什么？

下面是代码，应该怎么修改呢？

middlewares.py

    PROXIES = [
        {'ip_port': '**.**.**.**:8080', 'user_pass': ''},
        {'ip_port': '**.**.**.**:8080', 'user_pass': ''},
        {'ip_port': '**.**.**.**:8080', 'user_pass': ''}
    ]
    
    class ProxyMiddleware(object):
        def process_request(self, request, spider):
            proxy = random.choice(PROXIES)
            if proxy['user_pass'] is not None:
                request.meta['proxy'] = "http://%s" % proxy['ip_port']
                encoded_user_pass = base64.encodestring(proxy['user_pass'])
                request.headers['Proxy-Authorization'] = 'Basic ' + encoded_user_pass
                print("**************ProxyMiddleware have pass************" + proxy['ip_port'])
            else:
                print("**************ProxyMiddleware no pass************" + proxy['ip_port'])
                request.meta['proxy'] = "http://%s" % proxy['ip_port']

---

#coding=utf-8
import base64

#编码
encodestr = base64.b64encode("1234".encode(encoding='utf-8'))
print(encodestr) # 注意encodestr类型是byte,不是str
print(encodestr.decode())

#解码
decodestr = base64.b64decode(encodestr)
print(decodestr.decode())