The contents of `plugin/python_vimisort` is not a valid vimscript

[char101]

I am using this plugin with vim package on Windows and got this error:

Error detected while processing vim\package\40-filetype_python\isort\plugin\python_vimisort.vim:
line    1:
Traceback (most recent call last):
  File "<string>", line 1, in <module>
NameError: name '_vimisort' is not defined

Is that supposed to be a symlink or something? I think the right content of plugin\python_vimisort should be

runtime ftplugin\python_vimisort.vim