code: def add(self, repo, url):
          
          repo_name = []
          if not url.endswith("/"):
              url = url + "/"
          for line in self.custom_repositories_list.splitlines():
              line = line.lstrip()
              if line and not line.startswith("#"):
                  repo_name.append(line.split()[0])
          if (repo in self.meta.repositories or repo in repo_name or
                  repo in self.meta.default_repositories):
              print("\nRepository name '{0}' exist, select different name.\n"
                    "View all repositories with command 'slpkg "
                    "repo-list'.\n".format(repo))
              raise SystemExit()
          elif len(repo) > 6:
              print("\nslpkg: Error: Maximum repository name length must be "
                    "six (6) characters\n")
              raise SystemExit()
          with open(self.custom_repo_file, "a") as repos:
              new_line = "  {0}{1}{2}\n".format(repo, " " * (10 - len(repo)), url)
              repos.write(new_line)
          repos.close()
          print("\nRepository '{0}' successfully added\n".format(repo))
          raise SystemExit()
docs: Write custom repository name and url in a file