我正在练习“使用Python进行网页搜刮”中的代码，但始终遇到此证书问题：

from urllib.request import urlopen 
from bs4 import BeautifulSoup 
import re

pages = set()
def getLinks(pageUrl):
    global pages
    html = urlopen("http://en.wikipedia.org"+pageUrl)
    bsObj = BeautifulSoup(html)
    for link in bsObj.findAll("a", href=re.compile("^(/wiki/)")):
        if 'href' in link.attrs:
            if link.attrs['href'] not in pages:
                #We have encountered a new page
                newPage = link.attrs['href'] 
                print(newPage) 
                pages.add(newPage) 
                getLinks(newPage)
getLinks("")

错误是：

  File "/Library/Frameworks/Python.framework/Versions/3.7/lib/python3.7/urllib/request.py", line 1319, in do_open
    raise URLError(err)
urllib.error.URLError: <urlopen error [SSL: CERTIFICATE_VERIFY_FAILED] certificate verify failed: unable to get local issuer certificate (_ssl.c:1049)>

顺便说一句，我也在练习scrapy，但是不断出现问题：找不到命令：scrapy