centos上安装Python并修复yum

1，安装python3.7：
yum install zlib-devel bzip2-devel openssl-devel ncurses-devel sqlite-devel readline-devel tk-devel gcc make -y
wget https://www.python.org/ftp/python/3.7.0/Python-3.7.0a1.tgz
tar -xzvf Python-3.7.0a1.tgz
cd Python-3.7.0a1
./configure --prefix=/usr/local/python3.7
make && make altinstall，修改Python的环境变量
mv /usr/bin/python /usr/bin/python2.7.5
ln -s /usr/local/python3.7/bin/python3.7 /usr/bin/python，修复yum：
sed -i '1s/python/python2.7.5/' /usr/bin/yum
sed -i '1s/python/python2.7.5/' /usr/libexec/urlgrabber-ext-down