Created attachment 1489956 [details]
flat_network_error_message

Description of problem:
Not user-friendly message is appears during creating cloud "flat" network if Physical Network is already in use

Version-Release number of selected component (if applicable):
CFME 5.10.0.17 + OSP 14

How reproducible:
Always

Steps to Reproduce:
1. Login to the Cloudforms UI	
2. Navigate to Networks -> Networks	
3. Click configuration -> Add a new cloud network	
4. Select:
- Network Manager: Cloud provider
- Cloud Tenant: admin
- Provider Network Type: Flat
- Physical Network: (at a controller node execute the command: sudo docker exec -it neutron_api cat /etc/neutron/plugins/ml2/ml2_conf.ini | grep ^flat_networks)
- Network: test 
- Administrative State: Up	
5. Click add	Cloud Network "<Network Name>" created
6. Click configuration -> Add a new cloud network	
7. Select:
- Network Manager: Cloud provider
- Cloud Tenant: admin
- Provider Network Type: Flat
- Physical Network: (at a controller node execute the command: sudo docker exec -it neutron_api cat /etc/neutron/plugins/ml2/ml2_conf.ini | grep ^flat_networks)
- Network: my_flat_network
- Administrative State: Up	
8. Click add

Actual results:
Unable to create Cloud Network "my_flat_network": {"NeutronError": {"message": "Unable to create the flat network. Physical network datacentre is in use.", "type": "FlatNetworkInUse", "detail": ""}}

Expected results:
Unable to create Cloud Network "my_flat_network": Physical network "datacentre" is in use