def path_regex(self):
        """Return the regex for the path to the build folder."""
        build_dir = 'try-%(PLATFORM)s%(DEBUG)s/' % {
            'PLATFORM': self.platform_regex,
            'DEBUG': '-debug' if self.debug_build else ''}
        return urljoin(self.build_list_regex,
                       self.builds[self.build_index],
                       build_dir)
Return the regex for the path to the build folder.