hi,
i got the same message if i create a basic scene and change the render to redshift and open it on another version (where there's no redshift).
The problem maybe because the render is still pointing to redshift like so :

If you change the render to standard and remove the post effect (redshift) and save the file again, the message will no be show anymore.
You could probably run a script like this using c4dpy.exe to change the render engine and remove the videoPost effect :
Something like this.where 5709 seems to be the id of Redshift (I'm a bit surprised with this ID)
doc = c4d.documents.GetActiveDocument()
rd = doc.GetActiveRenderData()
rd[c4d.RDATA_RENDERENGINE] = c4d.RDATA_RENDERENGINE_STANDARD
vp = rd.GetFirstVideoPost()
while vp:
if vp.GetType() == 5709:
vp.Remove()
break;
vp = vp.GetNext()
c4d.EventAdd()
You should be able to load the document, make the changes and save it back.
Another idea, could be to create a dummy plugin of the time expected and just do nothing, but in that case, it's doesn't apply to python because you would need to create a post effect, or sometimes a SceneHook using c++, that's pretty easy and just a matter of a fiew click but another story for now.
Cheers,
Manuel.