Build on epel 6 stops with :
DEBUG util.py:450: Error: No Package found for libappstream-glib

I don't understand what you are asking us to do here. EPEL6 is outside of what this committee handles, as is a build error with some specific package.

No , but any package where we install appdata will not build in epel6 . if EPEL6 is outside of what this committee handle , I have to ask this in other place ...

Thanks

Indeed FPC is concerned with Fedora guidelines; we can't really change most things in RHEL and while we do try to keep macro compatibility and such via epel-rpm-macros, EPEL (and especially EPEL6) has diverged significantly in its packaging requirements.

EPEL-specific issues are generally documented https://fedoraproject.org/wiki/EPEL:Packaging; that's not maintained by this committee and is open for editing by all but I do occasionally move things there when they're still relevant to EPEL but have dropped out of the main packaging guidelines.

If the addition of a macro to EPEL6 could help maintain compatibility, then a bug filed against epel-rpm-macros would be useful.

Otherwise you'll just have to use a different specfile for EPEL6, or start getting used to having lots of conditional %if spaghetti in your spec. Packaging for really old distributions can be difficult.

OK , thanks for the help, it is fair, no worries , but epel6 is the second question (I just bring it here because have in common be about appdata), the first question is about guidelines in wiki/Packaging:AppData and new location of appdata breaks build in stable branches i.e F27 and F26 ...
While rawhide use /usr/data/metainfo/, F27 and F26 use /usr/data/appdata , if we change the rpm spec from /usr/data/appdata to /usr/data/metainfo/ as suggest in wiki, it will break the builds on F27 and F26 ( I think) .
For kf5 (kde framework) we have the work around of use %{_kf5_metainfodir}/ .

Best regards,

OK JFTR the solution is a scriplet like :

%if 0%{?fedora} || 0%{?rhel} > 6
BuildRequires: libappstream-glib
%endif