Fix bug causing all errors to be treated as unexpected

errors.ts

@@ -60,6 +60,8 @@ export class CodedError extends Error {
 
 	public constructor( errCode: ErrorCode, message?: string ) {
 		super( message );
+		// https://github.com/Microsoft/TypeScript-wiki/blob/master/Breaking-Changes.md#extending-built-ins-like-error-array-and-map-may-no-longer-work
+		Object.setPrototypeOf( this, CodedError.prototype );
 		this.errCode = errCode;
 	}
 }