The CentOS repository does not contain PySide. You can add the EPEL repository to your OS then use: yum install -y python-pyside and it will be installed on your system.
In order to install the EPEL repository for 64bit systems, run the following as root:
- cd /tmp
- wget http://download.fedoraproject.org/pub/epel/6/x86_64/epel-release-6-8.noarch.rpm
- rpm -ivh epel-release-6-8.noarch.rpm
If you're using a 32bit system, use the following in step 2:
wget http://download.fedoraproject.org/pub/epel/6/i386/epel-release-6-8.noarch.rpm