1. 确认网络配置和安全组设置是否正确，EC2实例是否具有互联网访问权限。
2. 检查URL地址是否正确。
3. 尝试使用AWS SDK或第三方库（如requests）代替urlib。

示例代码：

import urllib.request
from urllib.error import HTTPError, URLError

url = 'https://example.com'
try:
    response = urllib.request.urlopen(url)
    print(response.status)
except HTTPError as e:
    print('HTTP Error:', e.code)
except URLError as e:
    print('URL Error:', e.reason)
except Exception as e:
    print('Error:', str(e))

# 使用requests库的示例代码
import requests

url = 'https://example.com'
try:
    response = requests.get(url)
    print(response.status_code)
except requests.exceptions.RequestException as e:
    print('Error:', str(e))