I'm currently building a HDP 2.6 cluster on AWS with Ambari 2.5, just to learn the ropes. I didn't think twice about choosing RedHat 7 for my nodes. HDP 2.6 is supported on RedHat 7 alright, but now I read that Ambari 2.5 isn't.
Is that support underway?
By the way, Ambari server 2.5 doesn't seem to have a problem yet, but when installing the Ambari client it looks for Python 2.6 and RedHat 7.3 on AWS has Python 2.7.
Sorry for the late reaction. I missed your reactions. I'm sure RedHat 7.3 has Python 2.7 and I've tried it: it's the default. I don't have the cluster anymore at this moment. I switched to Ubuntu Server 16.04, because it was in all the support matrices. I might check that later when I build a new cluster with RedHat 7.3.