From 805368e902ada4c63e2e6e4d6692cf8cc2531a1e Mon Sep 17 00:00:00 2001
From: Marc Methot <mmethot@redhat.com>
Date: Tue, 16 Oct 2018 12:37:28 -0400
Subject: [PATCH] Handling unexpected python error "NoneType object is not
 iterable"

The glance documentation states that None (empty image) is a valid
return value. We have to handle this outcome. Adding error handling
helps debugging this unhandled issue

Change-Id: If7c22ac4516f8c2a6ccd8bf6b6ed98409312b138
Closes-Bug: #1798147
(cherry picked from commit d3afc39467c6532344118e8e491409878da9c2dd)
---
 cinder/exception.py    | 4 ++++
 cinder/image/glance.py | 4 ++++
 2 files changed, 8 insertions(+)

diff --git a/cinder/exception.py b/cinder/exception.py
index 0ed4e08d53d..d7bb818d9b3 100644
--- a/cinder/exception.py
+++ b/cinder/exception.py
@@ -727,6 +727,10 @@ class GlanceMetadataNotFound(NotFound):
     message = _("Glance metadata for volume/snapshot %(id)s cannot be found.")
 
 
+class ImageDownloadFailed(CinderException):
+    _msg_fmt = _("Failed to download image %(image_href)s, reason: %(reason)s")
+
+
 class ExportFailure(Invalid):
     message = _("Failed to export for volume: %(reason)s")
 
diff --git a/cinder/image/glance.py b/cinder/image/glance.py
index 476ca7f8552..ff6c1bc3101 100644
--- a/cinder/image/glance.py
+++ b/cinder/image/glance.py
@@ -357,6 +357,10 @@ class GlanceImageService(object):
         except Exception:
             _reraise_translated_image_exception(image_id)
 
+        if image_chunks is None:
+            raise exception.ImageDownloadFailed(
+                image_href=context, reason=_('image contains no data.'))
+
         if not data:
             return image_chunks
         else: