Gateway_less_FWD: NameError: global name 'db_dict' is not defined error while deleting allocation pool from virtual-router

Following exception is observed from api server while trying to delete allocation pool from virtual-router.

Traceback (most recent call last):
  File "/usr/lib/python2.7/dist-packages/vnc_cfg_api_server/vnc_cfg_api_server.py", line 3401, in _put_common
    ok, result = stateful_update()
  File "/usr/lib/python2.7/dist-packages/vnc_cfg_api_server/vnc_cfg_api_server.py", line 3357, in stateful_update
    prop_collection_updates=req_prop_coll_updates)
  File "/usr/lib/python2.7/dist-packages/vnc_cfg_api_server/vnc_cfg_types.py", line 2055, in pre_dbe_update
    db_conn)
  File "/usr/lib/python2.7/dist-packages/vnc_cfg_api_server/vnc_cfg_types.py", line 1955, in _vrouter_check_alloc_pool_delete
    iip_refs = db_dict.get('instance_ip_back_refs')
NameError: global name 'db_dict' is not defined

Build Info
----------
4.1.0.0-27 Mitaka

root@nodei15(controller):/usr/lib/python2.7/dist-packages/vnc_api# lsb_release -a
No LSB modules are available.
Distributor ID: Ubuntu
Description: Ubuntu 14.04.5 LTS
Release: 14.04
Codename: trusty
root@nodei15(controller):/usr/lib/python2.7/dist-packages/vnc_api#

Please see the complete log below:

>>> from vnc_api import vnc_api;from pprint import pprint;vnc_lib = vnc_api.VncApi(api_server_host = '10.204.217.127', auth_host ='10.204.217.127', username = 'admin', password = 'contrail123', tenant_name ='admin')

>>>
>>>
>>>
>>> nodek11_vr = vnc_lib.virtual_router_read(id="cc15ffd5-2008-4060-bc79-0dc3a3b3f6be")
irtual_router_update(nodek11_vr)
>>> project = vnc_lib.project_read(id="bd96af28-cd1e-4bd3-b673-9dbdf41dabb7")
>>>
>>> ipam0 = vnc_api.NetworkIpam('ipam0', project, vnc_api.IpamType("dhcp"),ipam_subnet_method='flat-subnet')
>>> vnc_lib.network_ipam_create(ipam0)
u'fc25a07b-2415-474e-b527-1894a4578d3b'
>>>
>>> sn1_pool_list = []
>>> sn1_pool_list.append(vnc_api.AllocationPoolType(start='11.1.1.16', end='11.1.1.18', vrouter_specific_pool=True))
>>>
>>> ipam0_sn1 = vnc_api.IpamSubnetType(subnet=vnc_api.SubnetType('11.1.1.0', 24), allocation_pools=sn1_pool_list, alloc_unit=1)
>>>
>>> ipam0.set_ipam_subnets(vnc_api.IpamSubnets([ipam0_sn1]))
>>> vnc_lib.network_ipam_update(ipam0)
u'{"network-ipam": {"href": "http://10.204.217.127:8082/network-ipam/fc25a07b-2415-474e-b527-1894a4578d3b", "uuid": "fc25a07b-2415-474e-b527-1894a4578d3b"}}'
>>>
>>> vr_subnet_list = []
>>> vr_subnet_list.append(vnc_api.SubnetType(ip_prefix='11.1.1.0',ip_prefix_len=24))
>>>
>>> vr_pool_list = []
>>> vr_pool_list.append(vnc_api.AllocationPoolType(start='11.1.1.16', end='11.1.1.18', vrouter_specific_pool=True))
>>> vr_ipam_type = vnc_api.VirtualRouterNetworkIpamType(vr_pool_list, vr_subnet_list)
>>>
>>> nodek11_vr.add_network_ipam(ipam0, vr_ipam_type)
>>> vnc_lib.virtual_router_update(nodek11_vr)

>>> pprint(vars(nodek11_vr))
{'_display_name': u'nodek11',
 '_id_perms': permissions = owner = cloud-admin, owner_access = 7, group = admin, group_access = 7, other_access = 7, uuid = uuid_mslong = 14705941449078751328, uuid_lslong = 13580901285228705470, enable = True, created = 2017-10-27T07:53:32.191127, last_modified = 2017-10-27T07:53:32.191127, description = None, user_visible = True, creator = None,
 '_original_network_ipam_refs': [],
 '_pending_field_list_updates': {},
 '_pending_field_map_updates': {},
 '_pending_field_updates': set([]),
 '_pending_ref_updates': set([]),
 '_perms2': owner = cloud-admin, owner_access = 7, global_access = 0, share = [],
 '_server_conn': <vnc_api.vnc_api.VncApi object at 0x7f82c79737d0>,
 '_type': 'virtual-router',
 '_uuid': u'cc15ffd5-2008-4060-bc79-0dc3a3b3f6be',
 '_virtual_router_dpdk_enabled': False,
 '_virtual_router_ip_address': u'10.204.216.231',
 'fq_name': [u'default-global-system-config', u'nodek11'],
 'name': u'nodek11',
 'network_ipam_refs': [{'attr': allocation_pools = [start = 11.1.1.16, end = 11.1.1.18, vrouter_specific_pool = True], subnet = [ip_prefix = 11.1.1.0, ip_prefix_len = 24],
                        'to': [u'default-domain', u'admin', 'ipam0'],
                        'uuid': u'fc25a07b-2415-474e-b527-1894a4578d3b'}],
 'parent_type': u'global-system-config',
 'parent_uuid': u'52bed2b0-d2cf-4353-9fd4-2f1c0919758b'}
>>>

>>> nodek11_vr.del_network_ipam(ipam0)
>>> vnc_lib.virtual_router_update(nodek11_vr)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/usr/lib/python2.7/dist-packages/vnc_api/vnc_api.py", line 42, in wrapper
    return func(self, *args, **kwargs)
  File "/usr/lib/python2.7/dist-packages/vnc_api/vnc_api.py", line 614, in _object_update
    'DELETE')
  File "/usr/lib/python2.7/dist-packages/vnc_api/vnc_api.py", line 42, in wrapper
    return func(self, *args, **kwargs)
  File "/usr/lib/python2.7/dist-packages/vnc_api/vnc_api.py", line 1080, in ref_update
    raise he
cfgm_common.exceptions.HttpError: HTTP Status: 500 Content: <type 'exceptions.NameError'>
Python 2.7.6: /usr/bin/python
Fri Oct 27 16:18:08 2017

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_api_server.py in _put_common(self=<vnc_cfg_api_server.vnc_cfg_api_server.VncApiServer object>, api_name='ref-update', obj_type='virtual_router', obj_uuid='cc15ffd5-2008-4060-bc79-0dc3a3b3f6be', db_obj_dict={'display_name': 'nodek11', 'fq_name': ['default-global-system-config', 'nodek11'], 'id_perms': {'created': '2017-10-27T07:53:32.191127', 'creator': None, 'description': None, 'enable': True, 'last_modified': '2017-10-27T10:45:22.722247', 'permissions': {'group': 'admin', 'group_access': 7, 'other_access': 7, 'owner': 'cloud-admin', 'owner_access': 7}, 'user_visible': True, 'uuid': {'uuid_lslong': 13580901285228705470L, 'uuid_mslong': 14705941449078751328L}}, 'network_ipam_refs': [{'attr': {'allocation_pools': [{'end': '11.1.1.18', 'start': '11.1.1.16'}], 'subnet': [{'ip_prefix': '11.1.1.0', 'ip_prefix_len': 24}]}, 'to': ['default-domain', 'admin', 'ipam0'], 'uuid': 'fc25a07b-2415-474e-b527-1894a4578d3b'}], 'parent_type': 'global-system-config', 'parent_uuid': '52bed2b0-d2cf-4353-9fd4-2f1c0919758b', 'perms2': {'global_access': 0, 'owner': 'cloud-admin', 'owner_access': 7, 'share': []}, 'uuid': 'cc15ffd5-2008-4060-bc79-0dc3a3b3f6be', 'virtual_router_dpdk_enabled': False, 'virtual_router_ip_address': '10.204.216.231'}, req_obj_dict={'network_ipam_refs': [], 'uuid': 'cc15ffd5-2008-4060-bc79-0dc3a3b3f6be'}, req_prop_coll_updates=None, ref_args={'data': {'attr': None}, 'operation': 'DELETE', 'ref_obj_type': 'network_ipam', 'ref_uuid': 'fc25a07b-2415-474e-b527-1894a4578d3b'}, quota_dict=None)
 3399
 3400 try:
 3401 ok, result = stateful_update()
 3402 except Exception as e:
 3403 ok = False
ok = False
result = 'RWX'
stateful_update = <function stateful_update>

 /usr/lib/python2.7/dist-packages/vnc_cfg_api_server/vnc_cfg_api_server.py in stateful_update()
 3355 (ok, result) = r_class.pre_dbe_update(
 3356 obj_uuid, obj_fq_name, req_obj_dict or {}, self._db_conn,
 3357 prop_collection_updates=req_prop_coll_updates)
 3358 if not ok:
 3359 return (ok, result)
prop_collection_updates undefined
req_prop_coll_updates = None

 /usr/lib/python2.7/dist-packages/vnc_cfg_api_server/vnc_cfg_types.py in pre_dbe_update(cls=<class 'vnc_cfg_api_server.vnc_cfg_types.VirtualRouterServer'>, id='cc15ffd5-2008-4060-bc79-0dc3a3b3f6be', fq_name=['default-global-system-config', 'nodek11'], obj_dict={'network_ipam_refs': [], 'uuid': 'cc15ffd5-2008-4060-bc79-0dc3a3b3f6be'}, db_conn=<vnc_cfg_api_server.vnc_db.VncDbClient object>, **kwargs={'prop_collection_updates': None})
 2053 (ok, db_dict) = cls.dbe_read(db_conn, 'virtual_router', id)
 2054 (ok, result) = cls._vrouter_check_alloc_pool_delete(db_dict, obj_dict,
 2055 db_conn)
 2056 if not ok:
 2057 return (False, (400, result))
db_conn = <vnc_cfg_api_server.vnc_db.VncDbClient object>

 /usr/lib/python2.7/dist-packages/vnc_cfg_api_server/vnc_cfg_types.py in _vrouter_check_alloc_pool_delete(self=<class 'vnc_cfg_api_server.vnc_cfg_types.VirtualRouterServer'>, db_vr_dict={'display_name': 'nodek11', 'fq_name': ['default-global-system-config', 'nodek11'], 'id_perms': {'created': '2017-10-27T07:53:32.191127', 'creator': None, 'description': None, 'enable': True, 'last_modified': '2017-10-27T10:45:22.722247', 'permissions': {'group': 'admin', 'group_access': 7, 'other_access': 7, 'owner': 'cloud-admin', 'owner_access': 7}, 'user_visible': True, 'uuid': {'uuid_lslong': 13580901285228705470L, 'uuid_mslong': 14705941449078751328L}}, 'network_ipam_refs': [{'attr': {'allocation_pools': [{'end': '11.1.1.18', 'start': '11.1.1.16'}], 'subnet': [{'ip_prefix': '11.1.1.0', 'ip_prefix_len': 24}]}, 'to': ['default-domain', 'admin', 'ipam0'], 'uuid': 'fc25a07b-2415-474e-b527-1894a4578d3b'}], 'parent_type': 'global-system-config', 'parent_uuid': '52bed2b0-d2cf-4353-9fd4-2f1c0919758b', 'perms2': {'global_access': 0, 'owner': 'cloud-admin', 'owner_access': 7, 'share': []}, 'uuid': 'cc15ffd5-2008-4060-bc79-0dc3a3b3f6be', 'virtual_machine_interfaces': [{'to': ['default-global-system-config', 'nodek11', 'vhost0'], 'uuid': 'b368ccfd-1910-4704-aa31-e37bd38db5ac'}], 'virtual_router_dpdk_enabled': False, ...}, req_vr_dict={'network_ipam_refs': [], 'uuid': 'cc15ffd5-2008-4060-bc79-0dc3a3b3f6be'}, db_conn=<vnc_cfg_api_server.vnc_db.VncDbClient object>)
 1953 ipam_refs = req_vr_dict.get('network_ipam_refs')
 1954 if not ipam_refs:
 1955 iip_refs = db_dict.get('instance_ip_back_refs')
 1956 if iip_refs:
 1957 return (False,
iip_refs undefined
db_dict undefined
<type 'exceptions.NameError'>: global name 'db_dict' is not defined
    __class__ = <type 'exceptions.NameError'>
    __delattr__ = <method-wrapper '__delattr__' of exceptions.NameError object>
    __dict__ = {}
    __doc__ = 'Name not found globally.'
    __format__ = <built-in method __format__ of exceptions.NameError object>
    __getattribute__ = <method-wrapper '__getattribute__' of exceptions.NameError object>
    __getitem__ = <method-wrapper '__getitem__' of exceptions.NameError object>
    __getslice__ = <method-wrapper '__getslice__' of exceptions.NameError object>
    __hash__ = <method-wrapper '__hash__' of exceptions.NameError object>
    __init__ = <method-wrapper '__init__' of exceptions.NameError object>
    __new__ = <built-in method __new__ of type object>
    __reduce__ = <built-in method __reduce__ of exceptions.NameError object>
    __reduce_ex__ = <built-in method __reduce_ex__ of exceptions.NameError object>
    __repr__ = <method-wrapper '__repr__' of exceptions.NameError object>
    __setattr__ = <method-wrapper '__setattr__' of exceptions.NameError object>
    __setstate__ = <built-in method __setstate__ of exceptions.NameError object>
    __sizeof__ = <built-in method __sizeof__ of exceptions.NameError object>
    __str__ = <method-wrapper '__str__' of exceptions.NameError object>
    __subclasshook__ = <built-in method __subclasshook__ of type object>
    __unicode__ = <built-in method __unicode__ of exceptions.NameError object>
    args = ("global name 'db_dict' is not defined",)
    message = "global name 'db_dict' is not defined"

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_api_server.py", line 3401, in _put_common
    ok, result = stateful_update()
  File "/usr/lib/python2.7/dist-packages/vnc_cfg_api_server/vnc_cfg_api_server.py", line 3357, in stateful_update
    prop_collection_updates=req_prop_coll_updates)
  File "/usr/lib/python2.7/dist-packages/vnc_cfg_api_server/vnc_cfg_types.py", line 2055, in pre_dbe_update
    db_conn)
  File "/usr/lib/python2.7/dist-packages/vnc_cfg_api_server/vnc_cfg_types.py", line 1955, in _vrouter_check_alloc_pool_delete
    iip_refs = db_dict.get('instance_ip_back_refs')
NameError: global name 'db_dict' is not defined