Raise more descriptive exception (#662)

Author: mvsusp

src/sagemaker/transformer.py

@@ -12,6 +12,8 @@
 # language governing permissions and limitations under the License.
 from __future__ import absolute_import
 
+from botocore import exceptions
+
 from sagemaker.job import _Job
 from sagemaker.session import Session
 from sagemaker.utils import base_name_from_image, name_from_base
@@ -119,8 +121,14 @@ def delete_model(self):
         self.sagemaker_session.delete_model(self.model_name)
 
     def _retrieve_image_name(self):
-        model_desc = self.sagemaker_session.sagemaker_client.describe_model(ModelName=self.model_name)
-        return model_desc['PrimaryContainer']['Image']
+        try:
+            model_desc = self.sagemaker_session.sagemaker_client.describe_model(ModelName=self.model_name)
+            return model_desc['PrimaryContainer']['Image']
+        except exceptions.ClientError:
+            raise ValueError('Failed to fetch model information for %s. '
+                             'Please ensure that the model exists. '
+                             'Local instance types require locally created models.'
+                             % self.model_name)
 
     def wait(self):
         self._ensure_last_transform_job()

tests/unit/test_transformer.py

@@ -16,6 +16,7 @@
 from mock import MagicMock, Mock, patch
 
 from sagemaker.transformer import Transformer, _TransformJob
+from tests.integ import test_local_mode
 
 MODEL_NAME = 'model'
 IMAGE_NAME = 'image-for-model'
@@ -65,6 +66,21 @@ def test_delete_model(sagemaker_session):
     sagemaker_session.delete_model.assert_called_with(MODEL_NAME)
 
 
+def test_transformer_fails_without_model():
+    transformer = Transformer(model_name='remote-model',
+                              sagemaker_session=test_local_mode.LocalNoS3Session(),
+                              instance_type='local',
+                              instance_count=1)
+
+    with pytest.raises(ValueError) as error:
+
+        transformer.transform('empty-data')
+
+    assert str(error.value) == 'Failed to fetch model information for remote-model. ' \
+                               'Please ensure that the model exists. ' \
+                               'Local instance types require locally created models.'
+
+
 @patch('sagemaker.transformer._TransformJob.start_new')
 def test_transform_with_all_params(start_new_job, transformer):
     content_type = 'text/csv'