Description of problem:
When e.g. installing a package via yum and one of the repos is not reachable yum
fails.

Version-Release number of selected component (if applicable):
yum-3.0-6

How reproducible:
make one of the repos not reachable (e.g via firewall) and try to install
package (from other repos)
  
Actual results:
yum fails and no package is installed

Expected results:
it should report the error but proceed to other repos

Additional info:

The actual output:

[root@erazim tmp]# yum install fubar
Loading "installonlyn" plugin
Setting up Install Process
Setting up repositories
http://ftp.belnet.be/packages/dries.ulyssis.org/fedora/linux/6/i386/dries/RPMS/repodata/repomd.xml:
[Errno 12] Timeout: <urlopen error timed out>
Trying other mirror.
Error: Cannot open/read repomd.xml file for repository: dries
[root@erazim tmp]# 


I have deliberately selected bogus package name to see what will happen. If one
of the repos is down user cannot even install security updates from the standard
repo.