Open Stack

I am installing openstack juno using packstack on centos7 on a one 
controller and two compute setup.

I am getting the following error :

Installing Dependencies                           [ ERROR ]

ERROR : Failed to run remote script, stdout: Loaded plugins: 
fastestmirror

stderr: Warning: Permanently added '10.129.2.57' (ECDSA) to the list of 
known hosts.
+ trap t ERR
+ yum install -y puppet hiera openssh-clients tar nc rubygem-json


  One of the configured repositories failed (Unknown),
  and yum doesn't have enough cached data to continue. At this point the 
only
  safe thing yum can do is fail. There are a few ways to work "fix" 
this:

      1. Contact the upstream for the repository and get them to fix the 
problem.

      2. Reconfigure the baseurl/etc. for the repository, to point to a 
working
         upstream. This is most often useful if you are using a newer
         distribution release than is supported by the repository (and 
the
         packages for the previous distribution release still work).

      3. Disable the repository, so yum won't use it by default. Yum 
will then
         just ignore the repository until you permanently enable it 
again or use
         --enablerepo for temporary usage:

             yum-config-manager --disable <repoid>

      4. Configure the failing repository to be skipped, if it is 
unavailable.
         Note that yum will try to contact the repo. when it runs most 
commands,
         so will have to try and fail each time (and thus. yum will be 
be much
         slower). If it is a very temporary problem though, this is 
often a nice
         compromise:

             yum-config-manager --save 
--setopt=<repoid>.skip_if_unavailable=true

Cannot find a valid baseurl for repo: base/7/x86_64
++ t
++ exit 1

Please check log file 
/var/tmp/packstack/20141226-155445-zPaWRI/openstack-setup.log for more 
information

I searched for this error online and found people facing this problem 
but no solution. Is it a puppet issue because my yum update is working?

Please help me in this regard.
Thanks,

Priyanka