SageMaker: correct describe_model_package_group does not exist msg (#7246)

Makefile

@@ -32,6 +32,7 @@ lint:
 
 format:
 	black moto/ tests/
+	ruff --fix moto/ tests/
 
 test-only:
 	rm -f .coverage

moto/sagemaker/models.py

@@ -3334,8 +3334,14 @@ class SageMakerModelBackend(BaseBackend):
     ) -> ModelPackageGroup:
         model_package_group = self.model_package_groups.get(model_package_group_name)
         if model_package_group is None:
+            model_package_group_arn = arn_formatter(
+                region_name=self.region_name,
+                account_id=self.account_id,
+                _type="model-package-group",
+                _id=f"{model_package_group_name}",
+            )
             raise ValidationError(
-                f"Model package group {model_package_group_name} not found"
+                f"ModelPackageGroup {model_package_group_arn} does not exist."
             )
         return model_package_group
 

tests/test_sagemaker/test_sagemaker_model_package_groups.py

@@ -4,6 +4,8 @@ from datetime import datetime
 from unittest import SkipTest
 
 import boto3
+import pytest
+from botocore.exceptions import ClientError
 from dateutil.tz import tzutc  # type: ignore
 from freezegun import freeze_time
 
@@ -193,6 +195,21 @@ def test_describe_model_package_group():
     assert resp["CreationTime"] == datetime(2020, 1, 1, 0, 0, 0, tzinfo=tzutc())
 
 
+@mock_sagemaker
+def test_describe_model_package_group_not_exists():
+    if settings.TEST_SERVER_MODE:
+        raise SkipTest("Can't freeze time in ServerMode")
+    client = boto3.client("sagemaker", region_name="eu-west-1")
+
+    with pytest.raises(ClientError) as e:
+        client.describe_model_package_group(
+            ModelPackageGroupName="test-model-package-group"
+        )
+
+    assert e.value.response["Error"]["Code"] == "ValidationException"
+    assert "does not exist" in e.value.response["Error"]["Message"]
+
+
 @mock_sagemaker
 def test_list_tags_model_package_group():
     region_name = "eu-west-1"