Comment 1 for bug 1387978

I don't see how we can handle it in heat, if it's a persistent failure, the best we can do is ignore it.

A possible option would be a --ignore-error option or similar which forces traversal of the whole stack even when we encounter an error (which is not sure to succeed because there may be a dependency on the thing which can't be deleted).

IMO this is a cinder bug, so it's probably best to debug the root cause of the delete volume error.