In Swift 3.0 (i.e. Xcode 8.0 or Xcode 8.1 beta 1), a call to fileReferenceURL does NOT give a file reference URL anymore... this code
ref = file:///Users/admin/
while it should have been printing
as it did, correctly, in Swift 2.2 (and before) in Xcode 7.3.1 for example.