[Fedora-packaging] sphinx-build to be used in %build or %install

[Parag Nemade]

Hi all,
    I am doing review of python-oslo-context which needs to build
documentation using sphinx-build command. I saw some python packages
providing documentation files are calling sphinx-build in %install
only.
   What will be the correct place to execute sphinx-build command in
%build or %install?

Regards,
Parag.