code: def rotate_eggs(self):
          
          # make sure the library directory exists
          if os.path.isdir(constants.insights_core_lib_dir):
              # make sure the newest.egg exists
              if os.path.isfile(constants.insights_core_newest):
                  # try copying newest to latest_stable
                  try:
                      # copy the core
                      shutil.move(constants.insights_core_newest,
                               constants.insights_core_last_stable)
                      # copy the core sig
                      shutil.move(constants.insights_core_gpg_sig_newest,
                               constants.insights_core_last_stable_gpg_sig)
                  except IOError:
                      message = ("There was a problem copying %s to %s." %
                                  (constants.insights_core_newest,
                                  constants.insights_core_last_stable))
                      logger.debug(message)
                      raise IOError(message)
                  return True
              else:
                  message = ("Cannot copy %s to %s because %s does not exist." %
                              (constants.insights_core_newest,
                              constants.insights_core_last_stable,
                              constants.insights_core_newest))
                  logger.debug(message)
                  return False
          else:
              logger.debug("Cannot copy %s to %s because the %s directory does not exist." %
                  (constants.insights_core_newest,
                      constants.insights_core_last_stable,
                      constants.insights_core_lib_dir))
              logger.debug("Try installing the Core first.")
              return False
docs: moves newest.egg to last_stable.egg
              this is used by the upload() function upon 2XX return
              returns (bool): if eggs rotated successfully
              raises (IOError): if it cant copy the egg from newest to last_stable