code: def lib_dir(self):
          
          if not self._lib_dir:
              lib_files = glob.glob("/usr/lib/*/librpm.so*")
              if not lib_files:
                  raise InstallError("Can not find lib directory.")
              self._lib_dir = os.path.dirname(lib_files[0])
          return self._lib_dir
docs: Return standard library directory path used by RPM libs.