tandoor-recipes: Fix formatting string

And clarify the message, since some of the URLs it refuses to try to
visit are just "#".

nixos/tests/tandoor-recipes-script-name.nix

@@ -78,7 +78,7 @@ import ./make-test-python.nix (
                         elif value.startswith("/"):
                             self.urls.append(f"{origin_url}{value}")
                         else:
-                            print("Ignoring external URL: {value}")
+                            print(f"Ignoring non-path URL: {value}")
 
                         break