解决 yum update 时遇到 Python 报错

当执行 yum update 时，出现 Python 报错，导致升级被中断。：

Traceback (most recent call last):
  File "/usr/libexec/urlgrabber-ext-down", line 75, in <module>
    main()
  File "/usr/libexec/urlgrabber-ext-down", line 61, in main
    fo = PyCurlFileObject(opts.url, opts.filename, opts)
  File "/usr/lib/python2.7/site-packages/urlgrabber/grabber.py", line 1258, in __init__
    self._do_open()
  File "/usr/lib/python2.7/site-packages/urlgrabber/grabber.py", line 1589, in _do_open
    self._do_grab()
  File "/usr/lib/python2.7/site-packages/urlgrabber/grabber.py", line 1723, in _do_grab
    self._do_perform()
  File "/usr/lib/python2.7/site-packages/urlgrabber/grabber.py", line 1517, in _do_perform
    raise KeyboardInterrupt
KeyboardInterrupt

一般情况是升级过程中，旧的库在调用某个库时遇到 bug，先单独升级报错的这个包，如上，先升级 urlgrabber：

$ sudo yum update python-urlgrabber

然后再继续更新系统。