Return package lists

def list_lib(self, repo):
        """Return package lists
        """
        packages = ""
        if repo == "sbo":
            if (os.path.isfile(
                    self.meta.lib_path + "{0}_repo/SLACKBUILDS.TXT".format(
                        repo))):
                packages = Utils().read_file(self.meta.lib_path + "{0}_repo/"
                                             "SLACKBUILDS.TXT".format(repo))
        else:
            if (os.path.isfile(
                    self.meta.lib_path + "{0}_repo/PACKAGES.TXT".format(repo))):
                packages = Utils().read_file(self.meta.lib_path + "{0}_repo/"
                                             "PACKAGES.TXT".format(repo))
        return packages