Mac安装 Scrapy 报错 No local packages or working download links found for incremental>=16.10.1

证书原因：

• wget http://curl.haxx.se/ca/cacert.pem
• mv cacert.pem ca-bundle.crt
• sudo mkdir -p /etc/pki/tls/certs/
• sudo cp ca-bundle.crt /etc/pki/tls/certs/