My build failed with
RPM build errors:
File not found: /root/rpmbuild/BUILDROOT/haproxy-1.5-dev25.1.x86_64/usr/share/man/man1/haproxy.1.gz
I had to change
%{_mandir}/man1/%{name}.1.gz
to
%{_mandir}/man1/%{name}.1
No clue is this fix really needed? But it worked for me.