centos 安装python3导致yum报错

 File "/usr/bin/yum", line 30
    except KeyboardInterrupt, e:

  File "/usr/libexec/urlgrabber-ext-down", line 28
    except OSError, e:

#!/usr/bin/python2
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:
...(以下省略)

#! /usr/bin/python2
#  A very simple external downloader
#  Copyright 2011-2012 Zdenek Pavlas

import time, os, errno, sys
from urlgrabber.grabber import \
    _readlines, URLGrabberOptions, _loads, \
    PyCurlFileObject, URLGrabError
...(以下省略)