code: def fixup_pth_and_egg_link(home_dir, sys_path=None):
      
      home_dir = os.path.normcase(os.path.abspath(home_dir))
      if sys_path is None:
          sys_path = sys.path
      for path in sys_path:
          if not path:
              path = '.'
          if not os.path.isdir(path):
              continue
          path = os.path.normcase(os.path.abspath(path))
          if not path.startswith(home_dir):
              logger.debug('Skipping system (non-environment) directory %s' % path)
              continue
          for filename in os.listdir(path):
              filename = os.path.join(path, filename)
              if filename.endswith('.pth'):
                  if not os.access(filename, os.W_OK):
                      logger.warn('Cannot write .pth file %s, skipping' % filename)
                  else:
                      fixup_pth_file(filename)
              if filename.endswith('.egg-link'):
                  if not os.access(filename, os.W_OK):
                      logger.warn('Cannot write .egg-link file %s, skipping' % filename)
                  else:
                      fixup_egg_link(filename)
docs: Makes .pth and .egg-link files use relative paths