disk: wrong status codes raise exceptions

disk.py

@@ -138,7 +138,9 @@ class Disk(object):
         disk_path = self.get_path()
         logger.info("Downloading image from %s to %s", url, disk_path)
         r = requests.get(url, stream=True)
-        if r.status_code == 200:
+        if r.status_code != 200:
+            raise Exception("Invalid response status code: %s" % r.status_code)
+
         class AbortException(Exception):
             pass
         if task.is_aborted():