Handle importing from a source archive; this also uses setup_requires
        but points easy_install directly to the source archive.

def get_local_file_dist(self):
        """
        Handle importing from a source archive; this also uses setup_requires
        but points easy_install directly to the source archive.
        """

        if not os.path.isfile(self.path):
            return

        log.info('Attempting to unpack and import astropy_helpers from '
                 '{0!r}'.format(self.path))

        try:
            dist = self._do_download(find_links=[self.path])
        except Exception as e:
            if DEBUG:
                raise

            log.warn(
                'Failed to import {0} from the specified archive {1!r}: '
                '{2}'.format(PACKAGE_NAME, self.path, str(e)))
            dist = None

        if dist is not None and self.auto_upgrade:
            # A version of astropy-helpers was found on the available path, but
            # check to see if a bugfix release is available on PyPI
            upgrade = self._do_upgrade(dist)
            if upgrade is not None:
                dist = upgrade

        return dist