【linux】 scrapy : Could not find a version that satisfies the requirement Twisted>=13.1.0 (from Scrapy) (from versions: )

centos7 + python3 安装 scrapy 时候报错，错误信息如下：

 Could not find a version that satisfies the requirement Twisted>=13.1.0 (from Scrapy) (from versions: )
No matching distribution found for Twisted>=13.1.0 (from Scrapy)

解决办法： 

官网下载： http://twistedmatrix.com/trac/wiki/Downloads

把下载的源码包上传到服务器  

cd /usr/local
# weget下载和解压的。我测试一直不成功，未找到原因，可能解锁姿势不对，我的方法是下载到本地。解压。上传到服务器的
cd Twisted-17.9.0
python setup.py install
cd .. 
pip3 install Scrapy #切记，S要大写