fix: include credential failure details

The Parameter Manager configuration error used a plain string with the exception placeholder left uninterpolated, so callers saw the literal placeholder instead of the default-credential exception that explained the failure. This interpolates the caught exception into the raised ValueError.

Co-authored-by: George Weale <gweale@google.com>
PiperOrigin-RevId: 949190934

Author: GWeale

src/google/adk/integrations/parameter_manager/parameter_client.py

@@ -96,7 +96,7 @@ def __init__(
       except Exception as e:
         raise ValueError(
             "'service_account_json' or 'auth_token' are both missing, and"
-            " error occurred while trying to use default credentials: {e}"
+            f" error occurred while trying to use default credentials: {e}"
         ) from e
 
     if not credentials:

tests/unittests/integrations/parameter_manager/test_parameter_client.py

@@ -163,7 +163,9 @@ def test_init_with_default_credentials_error(
     # Execute and verify
     with pytest.raises(
         ValueError,
-        match="error occurred while trying to use default credentials",
+        match=(
+            "error occurred while trying to use default credentials: Auth error"
+        ),
     ):
       ParameterManagerClient()