Install packages from official Slackware distribution

def start(self, is_upgrade):
        """
        Install packages from official Slackware distribution
        """
        self.case_insensitive()
        # fix if packages is for upgrade
        self.is_upgrade = is_upgrade
        mas_sum = dep_sum = sums = [0, 0, 0]
        self.msg.done()
        self.dependencies = self.resolving_deps()
        self.update_deps()
        (self.dep_dwn, self.dep_install, self.dep_comp_sum,
            self.dep_uncomp_sum) = self.store(self.dependencies)
        self.clear_masters()
        (self.dwn, self.install, self.comp_sum,
            self.uncomp_sum) = self.store(self.packages)
        if (self.meta.rsl_deps in ["on", "ON"] and
                "--resolve-off" not in self.flag):
            self.msg.done()
        if self.install:
            if self.matching and [""] != self.packages:
                self.msg.matching(self.packages)
            else:
                print("\nThe following packages will be automatically "
                      "installed or upgraded \nwith new version:\n")
            self.top_view()
            self.msg.upg_inst(self.is_upgrade)
            mas_sum = self.views(self.install, self.comp_sum)
            if self.dependencies:
                print("Installing for dependencies:")
                dep_sum = self.views(self.dep_install, self.dep_comp_sum)
            # sums[0] --> installed
            # sums[1] --> upgraded
            # sums[2] --> uninstall
            sums = [sum(i) for i in zip(mas_sum, dep_sum)]
            unit, size = units(self.comp_sum + self.dep_comp_sum,
                               self.uncomp_sum + self.dep_uncomp_sum)
            if self.matching and [""] != self.packages:
                print("\nMatching summary")
                print("=" * 79)
                print("Total {0} matching packages\n".format(sum(sums)))
                raise SystemExit(1)
            print("\nInstalling summary")
            print("=" * 79)
            print("{0}Total {1} {2}.".format(self.meta.color["GREY"],
                                             sum(sums),
                                             self.msg.pkg(sum(sums))))
            print("{0} {1} will be installed, {2} will be upgraded and "
                  "{3} will be reinstalled.".format(sums[2],
                                                    self.msg.pkg(sums[2]),
                                                    sums[1], sums[0]))
            print("Need to get {0} {1} of archives.".format(size[0],
                                                            unit[0]))
            print("After this process, {0} {1} of additional disk "
                  "space will be used.{2}".format(size[1], unit[1],
                                                  self.meta.color["ENDC"]))
            print("")
            self.if_all_installed()
            if self.msg.answer() in ["y", "Y"]:
                for inst, dwn in zip(self.dep_install + self.install,
                                     self.dep_dwn + self.dwn):
                    if (self.meta.not_downgrade == "on" and
                            self.not_downgrade(inst) is True):
                        continue
                    if (not os.path.isfile(self.meta.pkg_path + inst[:-4]) or
                            "--download-only" in self.flag or
                            "--reinstall" in self.flag):
                        Download(self.tmp_path, dwn.split(), self.repo).start()
                    else:
                        self.msg.template(78)
                        self.msg.pkg_found(inst)
                        self.msg.template(78)
                if "--download-only" in self.flag:
                    raise SystemExit()
                self.dep_install = Utils().check_downloaded(
                    self.tmp_path, self.dep_install)
                self.install = Utils().check_downloaded(
                    self.tmp_path, self.install)
                ins, upg = self.install_packages()
                self.msg.reference(ins, upg)
                write_deps(self.deps_dict)
                delete_package(self.tmp_path, self.dep_install + self.install)
        else:
            self.msg.not_found(self.is_upgrade)
            raise SystemExit(1)