code: def _assert_refspec(self):
          
          config = self.config_reader
          unset = 'placeholder'
          try:
              if config.get_value('fetch', default=unset) is unset:
                  msg = "Remote '%s' has no refspec set.\n"
                  msg += "You can set it as follows:"
                  msg += " 'git config --add \"remote.%s.fetch +refs/heads/*:refs/heads/*\"'."
                  raise AssertionError(msg % (self.name, self.name))
          finally:
              config.release()
docs: Turns out we can't deal with remotes if the refspec is missing