Description of problem:
I tried to run this command:
openstack network create --provider-network-type vlan  --provider-segment 10 --external --provider-physical-network datacentre nova

The error only says "Bad Request":
Error while executing command: Bad Request (HTTP 400) (Request-ID: req-3dcad903-149e-4252-b8db-f85c1ec77369)

In the neutron logs the error is: "The server could not comply with the request since it is either malformed or otherwise incorrect"


Version-Release number of selected component (if applicable):
openstack-neutron-11.0.2-1.el7ost.noarch


How reproducible:
100%


Steps to Reproduce:
1. Try to create a "vlan" network in a virutal environment, where the external network should be flat...


Actual results:
Unclear error message.


Expected results:
A more specific message, about what exactly failed so we can guess that the vlan doesn't exist...