若安装了Python3且没有删除Python2，那么启动yum命令会报错:

若安装了Python3且没有删除Python2，那么启动yum命令会报错:

  File "/usr/bin/yum", line 30
    except KeyboardInterrupt  e:
                              ^
SyntaxError: invalid syntax

情况一报错原因

这种情况的原因是yum配置文件解释器默认是/usr/bin/python，而安装Python3之后教程里一般会将这个软连接指向Python3所在的目录，也就是程序引用了错误的Python版本解释器，解决办法就将yum配置文件解释器指向原来的Python2版本:

vim /usr/bin/yum

#!/usr/bin/python # 修改之前

import sys

try:

     import yum

except ImportError: print >> sys.stderr, """\

There was a problem importing one of the Python modules

required to run yum. The error leading to this problem was:

#!/usr/bin/python2.7 # 修改之后

import sys

try:

     import yum except ImportError: print >> sys.stderr, """\

There was a problem importing one of the Python modules

required to run yum. The error leading to this problem was: