Use except x as y instead of except x, y

According to https://docs.python.org/3/howto/pyporting.html the
syntax changed in Python 3.x. The new syntax is usable with
Python >= 2.6 and should be preferred to be compatible with Python3.

Change-Id: I4a951aecc32ef9e5131da236ae4815b84897d67b
Use openstack-selinux on RHEL-7

Package openstack-selinux will be used on RHEL-7, so we need to install it

Change-Id: I82e233878a260eff6eec85aeed24ec986d0fda08
Merge "Use except x as y instead of except x, y"
Merge "Use openstack-selinux on RHEL-7"