Fail to destroy VM having Ceph/RBD volumes

[fangebee]

When trying to completely destroy a VM I got "Error 500" and the following stracktrace in logs:

  File "/srv/webvirtcloud/instances/views.py", line 408, in destroy 
    instance.proxy.delete_all_disks() 
  File "/srv/webvirtcloud/vrtManager/instance.py", line 1257, in delete_all_disks 
    self.refresh_instance_pools() 
  File "/srv/webvirtcloud/vrtManager/instance.py", line 1420, in refresh_instance_pools 
    self.get_wvmStorages().get_pool_by_target(target_path).refresh(0) 
AttributeError: 'NoneType' object has no attribute 'refresh'

This is because the VM has a disk on Ceph/RBD.