core: Fix creation of template-based HVM

core-modules/000QubesVm.py

@@ -1242,6 +1242,7 @@ class QubesVm(object):
         if os.path.exists (self.volatile_img):
            os.remove (self.volatile_img)
 
+        if hasattr(source_template, 'clean_volatile_img'):
             retcode = subprocess.call (["tar", "xf", source_template.clean_volatile_img, "-C", self.dir_path])
             if retcode != 0:
                 raise IOError ("Error while unpacking {0} to {1}".\