[Guidelines Change] Changes to the Packaging Guidelines

[Bill Nottingham]

Tom Callaway (tcallawa at redhat.com) said: 
> As part of the ongoing effort to update the guidelines for an eventual
> change from python2 to python3 as the default python we're promoting use
> of %{python2}, %{python2_sitelib}, and %{python2_sitearch} instead of
> the unversioned %{python}, %{python_sitelib}, and %{python_sitearch}
> macros. These macros are not available for EPEL5 and EPEL6. We've
> updated the Python Guidelines to mention conditionally defining those
> macros for EPEL5 and EPEL6 builds.

Given that EPEL controls epel-release, and epel-release is in
@buildsys-build, does it make sense to put macros like this in epel-release
itself for build uniformity?

Bill