I modiried JSON messages as above solution, however, other error messages were seen.

07/21/2015 05:53:47 PM [contrail-03:contrail-api:Config:0]: __default__ [SYS_ERR]: VncApiError: Failed to invoke type specific dbe_update_notification  
07/21/2015 05:53:47 PM [contrail-03:contrail-api:Config:0]: __default__ [SYS_ERR]: VncApiError: <type 'exceptions.AttributeError'>
Python 2.7.6: /usr/bin/python
Tue Jul 21 17:53:47 2015

A problem occurred in a Python script.  Here is the sequence of
function calls leading up to the error, in the order they occurred.

 /usr/lib/python2.7/dist-packages/vnc_cfg_api_server/vnc_cfg_ifmap.py in _dbe_subscribe_callback(self=<vnc_cfg_api_server.vnc_cfg_ifmap.VncServerKombuClient object>, oper_info={u'oper': u'UPDATE', u'type': u'virtual-network', u'uuid': u'00000000-9999-0000-0001-000000000001'})
  814                 self._dbe_create_notification(oper_info)
  815             if oper_info['oper'] == 'UPDATE':
  816                 self._dbe_update_notification(oper_info)
  817             elif oper_info['oper'] == 'DELETE':
  818                 self._dbe_delete_notification(oper_info)
self = <vnc_cfg_api_server.vnc_cfg_ifmap.VncServerKombuClient object>
self._dbe_update_notification = <bound method VncServerKombuClient._dbe_update_n...erver.vnc_cfg_ifmap.VncServerKombuClient object>>
oper_info = {u'oper': u'UPDATE', u'type': u'virtual-network', u'uuid': u'00000000-9999-0000-0001-000000000001'}

 /usr/lib/python2.7/dist-packages/vnc_cfg_api_server/vnc_cfg_ifmap.py in _dbe_update_notification(self=<vnc_cfg_api_server.vnc_cfg_ifmap.VncServerKombuClient object>, obj_info={u'oper': u'UPDATE', u'type': u'virtual-network', u'uuid': u'00000000-9999-0000-0001-000000000001'})
  876             r_class = self._db_client_mgr.get_resource_class(obj_info['type'])
  877             if r_class:
  878                 r_class.dbe_update_notification(obj_info)
  879         except:
  880             msg = "Failed to invoke type specific dbe_update_notification"
r_class = <class 'vnc_cfg_api_server.vnc_cfg_types.VirtualNetworkServer'>
r_class.dbe_update_notification = <bound method type.dbe_update_notification of <c..._api_server.vnc_cfg_types.VirtualNetworkServer'>>
obj_info = {u'oper': u'UPDATE', u'type': u'virtual-network', u'uuid': u'00000000-9999-0000-0001-000000000001'}

 /usr/lib/python2.7/dist-packages/vnc_cfg_api_server/vnc_cfg_types.py in dbe_update_notification(cls=<class 'vnc_cfg_api_server.vnc_cfg_types.VirtualNetworkServer'>, obj_ids={u'oper': u'UPDATE', u'type': u'virtual-network', u'uuid': u'00000000-9999-0000-0001-000000000001'})
  599     @classmethod
  600     def dbe_update_notification(cls, obj_ids):
  601         cls.addr_mgmt.net_update_notify(obj_ids)
  602     # end dbe_update_notification
  603 
cls = <class 'vnc_cfg_api_server.vnc_cfg_types.VirtualNetworkServer'>
cls.addr_mgmt = <vnc_cfg_api_server.vnc_addr_mgmt.AddrMgmt object>
cls.addr_mgmt.net_update_notify = <bound method AddrMgmt.net_update_notify of <vnc_cfg_api_server.vnc_addr_mgmt.AddrMgmt object>>
obj_ids = {u'oper': u'UPDATE', u'type': u'virtual-network', u'uuid': u'00000000-9999-0000-0001-000000000001'}

 /usr/lib/python2.7/dist-packages/vnc_cfg_api_server/vnc_addr_mgmt.py in net_update_notify(self=<vnc_cfg_api_server.vnc_addr_mgmt.AddrMgmt object>, obj_ids={u'oper': u'UPDATE', u'type': u'virtual-network', u'uuid': u'00000000-9999-0000-0001-000000000001'})
  512         vn_dict = result
  513         vn_fq_name_str = ':'.join(vn_dict['fq_name'])
  514         self._create_subnet_objs(vn_fq_name_str, vn_dict)
  515     # end net_update_notify
  516 
self = <vnc_cfg_api_server.vnc_addr_mgmt.AddrMgmt object>
self._create_subnet_objs = <bound method AddrMgmt._create_subnet_objs of <vnc_cfg_api_server.vnc_addr_mgmt.AddrMgmt object>>
vn_fq_name_str = u'default-domain:demo:testvn01'
vn_dict = {'display_name': u'testvn01', 'flood_unknown_unicast': True, 'fq_name': [u'default-domain', u'demo', u'testvn01'], 'id_perms': {u'created': u'2015-07-21T08:53:44.864508', u'creator': None, u'description': None, u'enable': True, u'last_modified': u'2015-07-21T08:53:46.405641', u'permissions': {u'group': u'admin', u'group_access': 7, u'other_access': 7, u'owner': u'admin', u'owner_access': 7}, u'user_visible': True, u'uuid': {u'uuid_lslong': 281474976710657, u'uuid_mslong': 2576941056}}, 'is_shared': False, 'network_ipam_refs': [{'attr': {u'ipam_subnets': [{u'addr_from_start': True, u'allocation_pools': [], u'default_gateway': u'30.1.1.253', u'dhcp_option_list': {...}, u'dns_server_address': u'30.1.1.2', u'enable_dhcp': True, u'host_routes': {...}, u'subnet': {...}, u'subnet_uuid': u'989f76ae-c86a-4c84-8d2f-84532fe9ad2d'}]}, 'href': 'http://0.0.0.0:9100/network-ipam/644962c8-b54f-497b-b3b1-7cb901fe59b6', 'to': [u'default-domain', u'default-project', u'default-network-ipam'], 'uuid': '644962c8-b54f-497b-b3b1-7cb901fe59b6'}], 'parent_href': u'http://0.0.0.0:9100/project/c05418b9-2f32-47f3-a085-a004dae65e49', 'parent_type': u'project', 'parent_uuid': 'c05418b9-2f32-47f3-a085-a004dae65e49', 'route_target_list': {u'route_target': [u'target:64512:30001']}, ...}

 /usr/lib/python2.7/dist-packages/vnc_cfg_api_server/vnc_addr_mgmt.py in _create_subnet_objs(self=<vnc_cfg_api_server.vnc_addr_mgmt.AddrMgmt object>, vn_fq_name_str=u'default-domain:demo:testvn01', vn_dict={'display_name': u'testvn01', 'flood_unknown_unicast': True, 'fq_name': [u'default-domain', u'demo', u'testvn01'], 'id_perms': {u'created': u'2015-07-21T08:53:44.864508', u'creator': None, u'description': None, u'enable': True, u'last_modified': u'2015-07-21T08:53:46.405641', u'permissions': {u'group': u'admin', u'group_access': 7, u'other_access': 7, u'owner': u'admin', u'owner_access': 7}, u'user_visible': True, u'uuid': {u'uuid_lslong': 281474976710657, u'uuid_mslong': 2576941056}}, 'is_shared': False, 'network_ipam_refs': [{'attr': {u'ipam_subnets': [{u'addr_from_start': True, u'allocation_pools': [], u'default_gateway': u'30.1.1.253', u'dhcp_option_list': {...}, u'dns_server_address': u'30.1.1.2', u'enable_dhcp': True, u'host_routes': {...}, u'subnet': {...}, u'subnet_uuid': u'989f76ae-c86a-4c84-8d2f-84532fe9ad2d'}]}, 'href': 'http://0.0.0.0:9100/network-ipam/644962c8-b54f-497b-b3b1-7cb901fe59b6', 'to': [u'default-domain', u'default-project', u'default-network-ipam'], 'uuid': '644962c8-b54f-497b-b3b1-7cb901fe59b6'}], 'parent_href': u'http://0.0.0.0:9100/project/c05418b9-2f32-47f3-a085-a004dae65e49', 'parent_type': u'project', 'parent_uuid': 'c05418b9-2f32-47f3-a085-a004dae65e49', 'route_target_list': {u'route_target': [u'target:64512:30001']}, ...})
  416                         dns_nameservers=nameservers,
  417                         alloc_pool_list=allocation_pools,
  418                         addr_from_start=addr_start)
  419                     self._subnet_objs[vn_fq_name_str][subnet_name] = \
  420                          subnet_obj
addr_from_start undefined
addr_start = True

 /usr/lib/python2.7/dist-packages/vnc_cfg_api_server/vnc_addr_mgmt.py in __init__(self=<vnc_cfg_api_server.vnc_addr_mgmt.Subnet object>, name=u'default-domain:demo:testvn01:30.1.1.0/24', prefix=u'30.1.1.0', prefix_len='24', gw=u'30.1.1.253', service_address=u'30.1.1.2', enable_dhcp=True, dns_nameservers=None, alloc_pool_list=[{'end': '30.1.1.254', 'start': '30.1.1.0'}], addr_from_start=True)
  248         # reserve excluded addresses
  249         for addr in exclude:
  250             self._db_conn.subnet_alloc_req(name, int(addr))
  251 
  252         self._name = name
self = <vnc_cfg_api_server.vnc_addr_mgmt.Subnet object>
self._db_conn = <vnc_cfg_api_server.vnc_cfg_ifmap.VncDbClient object>
self._db_conn.subnet_alloc_req = <bound method VncDbClient.subnet_alloc_req of <vnc_cfg_api_server.vnc_cfg_ifmap.VncDbClient object>>
name = u'default-domain:demo:testvn01:30.1.1.0/24'
builtinint = <type 'int'>
addr = IPAddress('30.1.1.253')

 /usr/lib/python2.7/dist-packages/vnc_cfg_api_server/vnc_cfg_ifmap.py in subnet_alloc_req(self=<vnc_cfg_api_server.vnc_cfg_ifmap.VncDbClient object>, subnet=u'default-domain:demo:testvn01:30.1.1.0/24', addr=503382525)
 1466 
 1467     def subnet_alloc_req(self, subnet, addr=None):
 1468         return self._zk_db.subnet_alloc_req(subnet, addr)
 1469     # end subnet_alloc_req
 1470 
self = <vnc_cfg_api_server.vnc_cfg_ifmap.VncDbClient object>
self._zk_db = <vnc_cfg_api_server.vnc_cfg_ifmap.VncZkClient object>
self._zk_db.subnet_alloc_req = <bound method VncZkClient.subnet_alloc_req of <vnc_cfg_api_server.vnc_cfg_ifmap.VncZkClient object>>
subnet = u'default-domain:demo:testvn01:30.1.1.0/24'
addr = 503382525

 /usr/lib/python2.7/dist-packages/vnc_cfg_api_server/vnc_cfg_ifmap.py in subnet_alloc_req(self=<vnc_cfg_api_server.vnc_cfg_ifmap.VncZkClient object>, subnet=u'default-domain:demo:testvn01:30.1.1.0/24', addr=503382525)
  991         try:
  992             if addr is not None:
  993                 if allocator.read(addr) is not None:
  994                     return addr
  995                 else:
allocator = None
allocator.read undefined
addr = 503382525
builtinNone = None
<type 'exceptions.AttributeError'>: 'NoneType' object has no attribute 'read'
    __class__ = <type 'exceptions.AttributeError'>
    __delattr__ = <method-wrapper '__delattr__' of exceptions.AttributeError object>
    __dict__ = {}
    __doc__ = 'Attribute not found.'
    __format__ = <built-in method __format__ of exceptions.AttributeError object>
    __getattribute__ = <method-wrapper '__getattribute__' of exceptions.AttributeError object>
    __getitem__ = <method-wrapper '__getitem__' of exceptions.AttributeError object>
    __getslice__ = <method-wrapper '__getslice__' of exceptions.AttributeError object>
    __hash__ = <method-wrapper '__hash__' of exceptions.AttributeError object>
    __init__ = <method-wrapper '__init__' of exceptions.AttributeError object>
    __new__ = <built-in method __new__ of type object>
    __reduce__ = <built-in method __reduce__ of exceptions.AttributeError object>
    __reduce_ex__ = <built-in method __reduce_ex__ of exceptions.AttributeError object>
    __repr__ = <method-wrapper '__repr__' of exceptions.AttributeError object>
    __setattr__ = <method-wrapper '__setattr__' of exceptions.AttributeError object>
    __setstate__ = <built-in method __setstate__ of exceptions.AttributeError object>
    __sizeof__ = <built-in method __sizeof__ of exceptions.AttributeError object>
    __str__ = <method-wrapper '__str__' of exceptions.AttributeError object>
    __subclasshook__ = <built-in method __subclasshook__ of type object>
    __unicode__ = <built-in method __unicode__ of exceptions.AttributeError object>
    args = ("'NoneType' object has no attribute 'read'",)
    message = "'NoneType' object has no attribute 'read'"

The above is a description of an error in a Python program.  Here is
the original traceback:

Traceback (most recent call last):
  File "/usr/lib/python2.7/dist-packages/vnc_cfg_api_server/vnc_cfg_ifmap.py", line 816, in _dbe_subscribe_callback
    self._dbe_update_notification(oper_info)
  File "/usr/lib/python2.7/dist-packages/vnc_cfg_api_server/vnc_cfg_ifmap.py", line 878, in _dbe_update_notification
    r_class.dbe_update_notification(obj_info)
  File "/usr/lib/python2.7/dist-packages/vnc_cfg_api_server/vnc_cfg_types.py", line 601, in dbe_update_notification
    cls.addr_mgmt.net_update_notify(obj_ids)
  File "/usr/lib/python2.7/dist-packages/vnc_cfg_api_server/vnc_addr_mgmt.py", line 514, in net_update_notify
    self._create_subnet_objs(vn_fq_name_str, vn_dict)
  File "/usr/lib/python2.7/dist-packages/vnc_cfg_api_server/vnc_addr_mgmt.py", line 418, in _create_subnet_objs
    addr_from_start=addr_start)
  File "/usr/lib/python2.7/dist-packages/vnc_cfg_api_server/vnc_addr_mgmt.py", line 250, in __init__
    self._db_conn.subnet_alloc_req(name, int(addr))
  File "/usr/lib/python2.7/dist-packages/vnc_cfg_api_server/vnc_cfg_ifmap.py", line 1468, in subnet_alloc_req
    return self._zk_db.subnet_alloc_req(subnet, addr)
  File "/usr/lib/python2.7/dist-packages/vnc_cfg_api_server/vnc_cfg_ifmap.py", line 993, in subnet_alloc_req
    if allocator.read(addr) is not None:
AttributeError: 'NoneType' object has no attribute 'read'