如何调试使用基本身份验证处理程序的urllib2请求

import urllib2
from urllib2 import HTTPError
from base64 import b64encode

def basic_auth_handler(user, password):
    password_mgr = urllib2.HTTPPasswordMgrWithDefaultRealm()
    password_mgr.add_password(None, "http://example.com", user, password)
    auth_handler = urllib2.HTTPBasicAuthHandler(password_mgr)
    return auth_handler

def proxy_handler(proxy_url, proxy_user=None, proxy_password=None):
    proxy_support = urllib2.ProxyHandler({"http": proxy_url})
    if proxy_user and proxy_password:
        proxy_auth_handler = urllib2.ProxyBasicAuthHandler()
        proxy_auth_handler.add_password(None, proxy_url, proxy_user, proxy_password)
        opener = urllib2.build_opener(proxy_support, proxy_auth_handler)
    else:
        opener = urllib2.build_opener(proxy_support)
    urllib2.install_opener(opener)

url = "http://example.com"
user = "your_username"
password = "your_password"

auth_handler = basic_auth_handler(user, password)
proxy_handler("http://proxy.example.com:8080", "proxy_user", "proxy_password")

opener = urllib2.build_opener(auth_handler)
urllib2.install_opener(opener)

try:
    response = urllib2.urlopen(url)
    print response.read()
except HTTPError as e:
    print "Error code:", e.code, " ", e.reason