Tricircle unit testcase can not pass as : Neither 'AnnotatedColumn' object nor 'Comparator' object has an attribute 'value'

ubuntu-bionic: Run tox
tox -epy27 -vv
non-zero return code
      File "/home/zuul/src/opendev.org/openstack/tricircle/.tox/py27/local/lib/python2.7/site-packages/neutron/db/ipam_pluggable_backend.py", line 598, in allocate_subnet
        subnet_request)
      File "/home/zuul/src/opendev.org/openstack/tricircle/.tox/py27/local/lib/python2.7/site-packages/neutron/db/ipam_backend_mixin.py", line 551, in _save_subnet
        context, network.id, subnet_args['ip_version'])
      File "/home/zuul/src/opendev.org/openstack/tricircle/.tox/py27/local/lib/python2.7/site-packages/neutron/objects/address_scope.py", line 47, in get_network_address_scope
        models_v2.Subnet.network_id == network_id)
      File "tricircle/tests/unit/utils.py", line 203, in filter
        values.extend([f.right.value for f in _filter])
      File "/home/zuul/src/opendev.org/openstack/tricircle/.tox/py27/local/lib/python2.7/site-packages/sqlalchemy/sql/elements.py", line 721, in __getattr__
        % (type(self).__name__, type(self.comparator).__name__, key)
    AttributeError: Neither 'AnnotatedColumn' object nor 'Comparator' object has an attribute 'value'

======
Totals
======
Ran: 253 tests in 23.0000 sec.
 - Passed: 235
 - Skipped: 0
 - Expected Fail: 0
 - Unexpected Success: 0
 - Failed: 18
Sum of execute time for each test: 74.0705 sec.

==============
Worker Balance
==============
 - Worker 0 (32 tests) => 0:00:03.965121
 - Worker 1 (32 tests) => 0:00:23.891324
 - Worker 2 (32 tests) => 0:00:02.295555
 - Worker 3 (32 tests) => 0:00:03.152569
 - Worker 4 (32 tests) => 0:00:20.029548
 - Worker 5 (31 tests) => 0:00:02.573248
 - Worker 6 (31 tests) => 0:00:16.789535
 - Worker 7 (31 tests) => 0:00:01.940497
ERROR: InvocationError for command /home/zuul/src/opendev.org/openstack/tricircle/.tox/py27/bin/stestr run (exited with code 1)
py27 finish: run-test after 31.32 seconds
py27 start: run-test-post
py27 finish: run-test-post after 0.00 seconds
___________________________________ summary ____________________________________
ERROR: py27: commands failed