Checking on two separate envs (one being a 16.1 ML2/OVS I had around), I saw that this command either always fails (privsep errors, etc), or once in a while hangs as described. This hang can be seen from running the command a few times. I am not sure what causes the hang but this may be follow up to neutron-sanity-check itself failing, anyway both are tracked in #1783195 Hopefully fixing the validation will be enough *** This bug has been marked as a duplicate of bug 1783195 ***