Change format of returning message

* When no free IP addresses are available in public network, Nailgun should
  return error message in a way which is acceptable by Fuel UI.
* Update corresponding unit test.

Change-Id: I9a2689c134bb4157d81f0749db495ec66d399118
Partial-bug: #1513774

nailgun/nailgun/api/v1/handlers/network_configuration.py

@@ -138,7 +138,12 @@ class ProviderHandler(BaseHandler):
         try:
             network_config = self.serializer.serialize_for_cluster(cluster)
         except errors.OutOfIPs as exc:
-            raise self.http(400, six.text_type(exc))
+            network_id = getattr(exc, 'network_id', None)
+            raise self.http(
+                400,
+                six.text_type(exc),
+                err_list=[{"errors": ["ip_ranges"], "ids": [network_id]}]
+            )
 
         if admin_nets != nm.get_admin_networks():
             try:

nailgun/nailgun/network/manager.py

@@ -538,8 +538,13 @@ class NetworkManager(object):
         ips_in_use = ips_in_use or set()
         ip_ranges = [IPRange(r.first, r.last)
                      for r in network_group.ip_ranges]
-        return cls.get_free_ips_from_ranges(
-            network_group.name, ip_ranges, ips_in_use, num)
+
+        try:
+            return cls.get_free_ips_from_ranges(
+                network_group.name, ip_ranges, ips_in_use, num)
+        except errors.OutOfIPs as exc:
+            exc.network_id = network_group.id
+            raise
 
     @classmethod
     def _get_ips_except_admin(cls, node_id=None,

nailgun/nailgun/test/integration/test_network_configuration.py

@@ -610,6 +610,10 @@ class TestNeutronNetworkConfigurationHandler(BaseIntegrationTest):
             "Not enough free IP addresses in ranges [172.16.0.19-172.16.0.19] "
             "of 'public' network",
             resp.json_body['message'])
+        self.assertEqual(
+            [{'errors': ["ip_ranges"], 'ids': [public['id']]}],
+            resp.json_body['errors']
+        )
 
     def test_assign_vip_in_correct_node_group(self):
         # prepare two nodes that are in different node groups