Find all available InstallationCandidate for project_name

        This checks index_urls and find_links.
        All versions found are returned as an InstallationCandidate list.

        See _link_package_versions for details on which files are accepted

def find_all_candidates(self, project_name):
        # type: (str) -> List[Optional[InstallationCandidate]]
        """Find all available InstallationCandidate for project_name

        This checks index_urls and find_links.
        All versions found are returned as an InstallationCandidate list.

        See _link_package_versions for details on which files are accepted
        """
        index_locations = self._get_index_urls_locations(project_name)
        index_file_loc, index_url_loc = self._sort_locations(index_locations)
        fl_file_loc, fl_url_loc = self._sort_locations(
            self.find_links, expand_dir=True,
        )

        file_locations = (Link(url) for url in itertools.chain(
            index_file_loc, fl_file_loc,
        ))

        # We trust every url that the user has given us whether it was given
        #   via --index-url or --find-links.
        # We want to filter out any thing which does not have a secure origin.
        url_locations = [
            link for link in itertools.chain(
                (Link(url) for url in index_url_loc),
                (Link(url) for url in fl_url_loc),
            )
            if self._validate_secure_origin(logger, link)
        ]

        logger.debug('%d location(s) to search for versions of %s:',
                     len(url_locations), project_name)

        for location in url_locations:
            logger.debug('* %s', location)

        canonical_name = canonicalize_name(project_name)
        formats = self.format_control.get_allowed_formats(canonical_name)
        search = Search(project_name, canonical_name, formats)
        find_links_versions = self._package_versions(
            # We trust every directly linked archive in find_links
            (Link(url, '-f') for url in self.find_links),
            search
        )

        page_versions = []
        for page in self._get_pages(url_locations, project_name):
            try:
                logger.debug('Analyzing links from page %s', page.url)
            except AttributeError:
                continue
            with indent_log():
                page_versions.extend(
                    self._package_versions(page.iter_links(), search)
                )

        file_versions = self._package_versions(file_locations, search)
        if file_versions:
            file_versions.sort(reverse=True)
            logger.debug(
                'Local files found: %s',
                ', '.join([
                    url_to_path(candidate.location.url)
                    for candidate in file_versions
                ])
            )

        # This is an intentional priority ordering
        return file_versions + find_links_versions + page_versions