def METHOD_NAME(project, branch_list):
    """
    Build the branches for a specific project.
    Returns:
        to_build - a list of branches that were built
        not_building - a list of branches that we won't build
    """
    to_build = set()
    not_building = set()
    for branch in branch_list:
        versions = project.versions_from_branch_name(branch)
        for version in versions:
            log.debug(
                'Processing.',
                project_slug=project.slug,
                version_slug=version.slug,
            )
            ret = _build_version(project, version.slug, already_built=to_build)
            if ret:
                to_build.add(ret)
            else:
                not_building.add(version.slug)
    return (to_build, not_building)