Merge pull request #862 from dhermes/fix-blob-exists

Making Blob.exists() work as Bucket.exists().

gcloud/storage/api.py

@@ -126,7 +126,7 @@ def list_buckets(project=None, max_results=None, page_token=None, prefix=None,
     # class has it as a reserved property.
     if page_token is not None:
         result.next_page_token = page_token
-    return iter(result)
+    return result
 
 
 def get_bucket(bucket_name, connection=None):

gcloud/storage/blob.py

@@ -226,9 +226,14 @@ def exists(self, connection=None):
             # We only need the status code (200 or not) so we seek to
             # minimize the returned payload.
             query_params = {'fields': 'name'}
+            # We intentionally pass `_target_object=None` since fields=name
+            # would limit the local properties.
             connection.api_request(method='GET', path=self.path,
                                    query_params=query_params,
-                                   _target_object=self)
+                                   _target_object=None)
+            # NOTE: This will not fail immediately in a batch. However, when
+            #       Batch.finish() is called, the resulting `NotFound` will be
+            #       raised.
             return True
         except NotFound:
             return False