pip安装jieba报错：
Could not fetch URL https://pypi.tuna.tsinghua.edu.cn/simple/gevent/: There was a problem confirming the ssl certificate: HTTPSConnectionPool(host='pypi.tuna.tsinghua.edu.cn', port=443): Max retries exceeded with url: /simple/gevent/ (Caused by SSLError(SSLError(1, u'[SSL: CERTIFICATE_VERIFY_FAILED] certificate verify failed (_ssl.c:727)'),)) - skipping
ERROR: Could not find a version that satisfies the requirement gevent (from versions: none)
ERROR: No matching distribution found for gevent
解决方式：
通过-i参数指定源直接下载
pip --trusted-host pypi.tuna.tsinghua.edu.cn install -i https://pypi.tuna.tsinghua.edu.cn/simple jieba
