Latest RPM for XtraDB cluster client Percona-XtraDB-Cluster-client-56-5.6.20-25.7.888.el6.x86_64 does not provides mysql on CentOS/RHEL 6
The consequence is that the corresponding Percona-XtraDB-Cluster-server, which requires mysql will ask to install RPM mysql as a requisite for RPM perl-DBD-MySQL-4.022-1.el6.rfx.x86_64 and of course mysql conflicts with Percona-XtraDB-Cluster-client-56
As we can see here previous version of Percona cluster client provided mysql, and the client-56-5.6.20-25.7.888 is missing !
yum provides mysql |grep Percona-XtraDB-Cluster-client-56-5.6 |sort
1:Percona-XtraDB-Cluster-client-56-5.6.14-25.1.570.rhel6.x86_64 : Percona XtraDB
1:Percona-XtraDB-Cluster-client-56-5.6.14-25.1.571.rhel6.x86_64 : Percona XtraDB
1:Percona-XtraDB-Cluster-client-56-5.6.15-25.2.645.rhel6.x86_64 : Percona XtraDB
1:Percona-XtraDB-Cluster-client-56-5.6.15-25.2.692.rhel6.x86_64 : Percona XtraDB
1:Percona-XtraDB-Cluster-client-56-5.6.15-25.3.706.rhel6.x86_64 : Percona XtraDB
1:Percona-XtraDB-Cluster-client-56-5.6.15-25.4.731.rhel6.x86_64 : Percona XtraDB
1:Percona-XtraDB-Cluster-client-56-5.6.15-25.5.759.rhel6.x86_64 : Percona XtraDB
1:Percona-XtraDB-Cluster-client-56-5.6.19-25.6.824.el6.x86_64 : Percona XtraDB
I had to install previous version of cluster client and server to be able to install without dependency conflict