报错：
**/usr/bin/yum: line 3: import: command not found
/usr/bin/yum: line 4: try:: command not found
/usr/bin/yum: line 5: import: command not found
/usr/bin/yum: line 6: except: command not found
/usr/bin/yum: line 24: syntax error near unexpected token `('
/usr/bin/yum: line 24: `""" % (sys.exc_value, sys.version)'**
原因：升级python3导致
解决方式：
修改文件/usr/bin/yum、头中相应python为#!/usr/bin/python2.7
