It seems like the folder is missing from the project and the resources folder.
Running into the same issue.
The error I am getting is
"Build input file cannot be found: ‘~/ARKit_by_Tutorials_v2.0/14-getting-started-face-ar/starter/RWFaceCase/RWFaceCase/Models.scnassets’
and I can see that file/folder does not exist.
Just copying the folder from Chapter 15 got rid of the error.