Type 'Error' does not conform to protocol 'RawRepresentable'

The problem is that you've named your error type Error – which conflicts with the standard library Error protocol (therefore Swift thinks you've got a circular reference).

You could refer to the Swift Error protocol as Swift.Error in order to disambiguate:

enum Error : Swift.Error {
    case NotFound
}

But this will mean that any future references to Error in your module will refer to your Error type, not the Swift Error protocol (you'll have to disambiguate again).

Therefore the easiest solution by far would be simply renaming your error type to something more descriptive.

This error occurs because you are "overriding" the existing declaration ofError which is a protocol. So you have to choose another (probably more descriptive) name for your "Error" enum.