code: def convert_path(pathname):
      
      if os.sep == '/':
          return pathname
      if not pathname:
          return pathname
      if pathname[0] == '/':
          raise ValueError("path '%s' cannot be absolute" % pathname)
      if pathname[-1] == '/':
          raise ValueError("path '%s' cannot end with '/'" % pathname)
  
      paths = pathname.split('/')
      while os.curdir in paths:
          paths.remove(os.curdir)
      if not paths:
          return os.curdir
      return os.path.join(*paths)
docs: Return 'pathname' as a name that will work on the native filesystem.
  
      The path is split on '/' and put back together again using the current
      directory separator.  Needed because filenames in the setup script are
      always supplied in Unix style, and have to be converted to the local
      convention before we can actually use them in the filesystem.  Raises
      ValueError on non-Unix-ish systems if 'pathname' either starts or
      ends with a slash.