I keep getting this message in Xcode 8.2 with a project with SceneKit assets in a .scnassets folder. I have no idea if this is occuring elsewhere, I just know it’s when I update the images in my .scnassets folder. There is, for me, a simple fix.
Simply navigate via terminal to your project folder then run the command:
xattr -rc .
Following this, nip back into Xcode and perform a quick clean and build and hopefully the issue is gone.