有時使用yum install時會出現如下錯誤，導致軟件無法安裝。

Loaded plugins: fastestmirror
Cleaning repos: base epel extras mysql-connectors-community mysql-tools-community
: mysql56-community updates
14 metadata files removed
0 sqlite files removed
0 metadata files removed
Loaded plugins: fastestmirror
base | 3.6 kB 00:00:00
epel | 4.7 kB 00:00:00
extras | 3.4 kB 00:00:00
mysql-connectors-community | 2.5 kB 00:00:00
mysql-tools-community | 2.5 kB 00:00:00
mysql56-community | 2.5 kB 00:00:00
updates | 3.4 kB 00:00:00
File "/usr/libexec/urlgrabber-ext-down", line 28
except OSError, e:
^
SyntaxError: invalid syntax
File "/usr/libexec/urlgrabber-ext-down", line 28
except OSError, e:
^
SyntaxError: invalid syntax
File "/usr/libexec/urlgrabber-ext-down", line 28
except OSError, e:
^
SyntaxError: invalid syntax
File "/usr/libexec/urlgrabber-ext-down", line 28
except OSError, e:
^
SyntaxError: invalid syntax
File "/usr/libexec/urlgrabber-ext-down", line 28
except OSError, e:
^
SyntaxError: invalid syntax

Exiting on user cancel

這個yum的一個bug，解決的辦法是修改/usr/lib/python2.7/site-packages/urlgrabber/grabber.py文件。

elif errcode == 42:
　　# this is probably wrong but ultimately this is what happens
　　# we have a legit http code and a pycurl ‘writer failed‘ code
　　# which almost always means something aborted it from outside
　　# since we cannot know what it is -I‘m banking on it being
　　# a ctrl-c. XXXX - if there‘s a way of going back two raises to
　　# figure out what aborted the pycurl process FIXME
　　raise KeyboardInterrupt

修改後：

#elif errcode == 42:
　　# this is probably wrong but ultimately this is what happens
　　# we have a legit http code and a pycurl ‘writer failed‘ code
　　# which almost always means something aborted it from outside
　　# since we cannot know what it is -I‘m banking on it being
　　# a ctrl-c. XXXX - if there‘s a way of going back two raises to
　　# figure out what aborted the pycurl process FIXME
　　#raise KeyboardInterrupt

然後切換到root用戶，執行以下命令：

yum clean metadata

yum clean all

yum upgrade

執行完後，重新執行安裝命令，大多數人應該都解決了，但是博主運氣較差，並沒有解決。

後來各種鼓搗，又修改了/usr/bin/yum文件，將第一行修改為如下內容：

#!/usr/bin/python2

但是新問題又來了：

[root@iz2ze3g36wzfbgvzqas89uz conf]# yum -y install php
File "/usr/bin/yum", line 30
except KeyboardInterrupt, e:
^
SyntaxError: invalid syntax

解決方法就是，修改/usr/libexec/urlgrabber-ext-down文件，將第一行修改為如下內容：

#! /usr/bin/python2

至此，終於可以愉快的安裝軟件了。

Linux下使用yum install時出現Exiting on user cancel