small validation error message formatting fix

aea/configurations/validation.py

@@ -243,7 +243,7 @@ def _validate(self, instance: Dict) -> None:
     @staticmethod
     def _build_message_from_errors(errors: List[jsonschema.ValidationError]) -> str:
         """Build an error message from validation errors."""
-        path = lambda error: ".".join(list(error.path))  # noqa # type: ignore
+        path = lambda error: "::".join(map(str, error.path))  # noqa
         result = [f"{path(error)}: {error.message}" for error in errors]
         return "The following errors occurred during validation:\n - " + "\n - ".join(
             result