ISO 5.1.2 staging jobs failure due to: 'NoneType' object has no attribute '__getitem__'

http://jenkins-product.srt.mirantis.net:8080/job/5.1.2.staging.ubuntu.bvt_2/96/
http://jenkins-product.srt.mirantis.net:8080/view/Staging%20Mirrors/job/5.1.2.test_staging_mirror/107/

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ERROR: Deploy cluster in HA mode with VLAN Manager
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Traceback (most recent call last):
  File "/home/jenkins/venv-nailgun-tests/local/lib/python2.7/site-packages/proboscis/case.py", line 296, in testng_method_mistake_capture_func
    compatability.capture_type_error(s_func)
  File "/home/jenkins/venv-nailgun-tests/local/lib/python2.7/site-packages/proboscis/compatability/exceptions_2_6.py", line 27, in capture_type_error
    func()
  File "/home/jenkins/venv-nailgun-tests/local/lib/python2.7/site-packages/proboscis/case.py", line 350, in func
    func(test_case.state.get_state())
  File "/home/jenkins/workspace/5.1.2.staging.ubuntu.bvt_2/fuelweb_test/helpers/decorators.py", line 52, in wrapper
    return func(*args, **kwagrs)
  File "/home/jenkins/workspace/5.1.2.staging.ubuntu.bvt_2/fuelweb_test/tests/test_ha.py", line 83, in deploy_ha_vlan
    self.env.nodes().slaves[0])
  File "/home/jenkins/workspace/5.1.2.staging.ubuntu.bvt_2/fuelweb_test/__init__.py", line 48, in wrapped
    result = func(*args, **kwargs)
  File "/home/jenkins/workspace/5.1.2.staging.ubuntu.bvt_2/fuelweb_test/models/fuel_web_client.py", line 1298, in get_nailgun_primary_controller
    fqdn, self.environment.nodes().slaves)
  File "/home/jenkins/workspace/5.1.2.staging.ubuntu.bvt_2/fuelweb_test/__init__.py", line 48, in wrapped
    result = func(*args, **kwargs)
  File "/home/jenkins/workspace/5.1.2.staging.ubuntu.bvt_2/fuelweb_test/models/fuel_web_client.py", line 515, in find_devops_node_by_nailgun_fqdn
    macs = {i['mac'] for i in nailgun_node['meta']['interfaces']}
TypeError: 'NoneType' object has no attribute '__getitem__'

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Ran 4 tests in 4598.867s

FAILED (errors=1)