def is_build_dir(self, folder_name):
        """Return whether or not the given dir contains a build."""
        # Cannot move up to base scraper due to parser.entries call in
        # get_build_info_for_date (see below)

        url = '%s/' % urljoin(self.base_url, self.monthly_build_list_regex, folder_name)
        if self.application in APPLICATIONS_MULTI_LOCALE \
                and self.locale != 'multi':
            url = '%s/' % urljoin(url, self.locale)

        parser = self._create_directory_parser(url)

        pattern = re.compile(self.binary_regex, re.IGNORECASE)
        for entry in parser.entries:
            try:
                pattern.match(entry).group()
                return True
            except Exception:
                # No match, continue with next entry
                continue
        return False
Return whether or not the given dir contains a build.