yum is broken after upgrade python from 2.x to 3.x on CentOS 7

yum is broken after upgrade python from 2.x to 3.x on CentOS7:

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

Resolution: modify /usr/bin/yum and /usr/libexec/urlgrabber-ext-down, change first line from “#!/usr/bin/python” to “#!/usr/bin/python2”:

#!/usr/bin/python2
import sys
try:
    import yum
except ImportError:
    print >> sys.stderr, """\
...

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

#   This library is free software; you can redistribute it and/or
#   modify it under the terms of the GNU Lesser General Public