code: def _resolve_setup_path(egg_base, install_dir, egg_path):
          
          path_to_setup = egg_base.replace(os.sep, '/').rstrip('/')
          if path_to_setup != os.curdir:
              path_to_setup = '../' * (path_to_setup.count('/') + 1)
          resolved = pkg_resources.normalize_path(
              os.path.join(install_dir, egg_path, path_to_setup)
          )
          if resolved != pkg_resources.normalize_path(os.curdir):
              raise DistutilsOptionError(
                  "Can't get a consistent path to setup script from"
                  " installation directory", resolved,
                  pkg_resources.normalize_path(os.curdir))
          return path_to_setup
docs: Generate a path from egg_base back to '.' where the
          setup script resides and ensure that path points to the
          setup path from $install_dir/$egg_path.