'Create a package finder appropriate to this requirement command.'

def _build_package_finder(self, options, session):

    index_urls = ([options.index_url] + options.extra_index_urls)
    if options.no_index:
        logger.info('Ignoring    indexes:    %s', ','.join(index_urls))
        index_urls = []
    return PackageFinder(find_links=options.find_links, format_control=options.format_control, index_urls=index_urls, trusted_hosts=options.trusted_hosts, allow_all_prereleases=options.pre, process_dependency_links=options.process_dependency_links, session=session)
