(gcloud.app.deploy) Error Response: [13] An internal error occurred

Question

I've been deploying an Angular 4 app to app engine for weeks and yesterday it stopped deploying. Even after checking the GCP log and verbosity=debug, all I can get is "Error Response: [13] An internal error occurred." I've updated NPM and gcloud components.

How do I debug this?

Updating service [default]...\DEBUG: Operation [apps/project-99999/operations/48dda4a4-9f4b-4144-8085-9c] complete. Result: {
    "metadata": {
        "target": "apps/project-99999/services/default/versions/201705635", 
        "method": "google.appengine.v1.Versions.CreateVersion", 
        "user": "user@gmail.com", 
        "insertTime": "2017-08-21T20:56:41.587Z", 
        "ephemeralMessage": "Copying 97 application files and 48 static files.", 
        "endTime": "2017-08-21T20:56:45.511Z", 
        "@type": "type.googleapis.com/google.appengine.v1.OperationMetadataV1"
    }, 
    "done": true, 
    "name": "apps/project-99999/operations/48dda4a4-9f4b-4144-8085-9c1a", 
    "error": {
        "message": "An internal error occurred.", 
        "code": 13
    }
}
Updating service [default]...failed.                                                                               
DEBUG: (gcloud.app.deploy) Error Response: [13] An internal error occurred.
Traceback (most recent call last):
  File "/Users/user/GitHub/google-cloud-sdk/lib/googlecloudsdk/calliope/cli.py", line 787, in Execute
    resources = args.calliope_command.Run(cli=self, args=args)

Answer 1

Arghh, I accidentally left the macOS "Icon?" file in the assets folder and it wasn't in my .gitignore. Simply deleting the file solved the problem. Unbelievable... although a nice descriptive error message sure would have been nice.

Answer 2

I didn't have an Icon* file but a .keep file. Added .keep to .gitignore and redeployed successfully.