python-fuelclient tests fail in gate-python-fuelclient-python27-ubuntu-xenial and gate-python-fuelclient-python27-ubuntu-trusty

Detailed bug description:
Test fuelclient.tests.unit.v2.cli.test_node.TestNodeCommand.test_node_list_ansible_inventory fails in gate-python-fuelclient-python27-ubuntu-xenial.
Console output (http://logs.openstack.org/00/355600/1/check/gate-python-fuelclient-python27-ubuntu-xenial/950c351/console.html):

2016-08-16 04:11:15.195278 | ==============================
2016-08-16 04:11:15.195316 | Failed 1 tests - output below:
2016-08-16 04:11:15.195348 | ==============================
2016-08-16 04:11:15.195362 |
2016-08-16 04:11:15.195443 | fuelclient.tests.unit.v2.cli.test_node.TestNodeCommand.test_node_list_ansible_inventory
2016-08-16 04:11:15.195508 | ---------------------------------------------------------------------------------------
2016-08-16 04:11:15.195522 |
2016-08-16 04:11:15.195581 | Captured traceback:
2016-08-16 04:11:15.195614 | ~~~~~~~~~~~~~~~~~~~
2016-08-16 04:11:15.195649 | Traceback (most recent call last):
2016-08-16 04:11:15.195719 | File "fuelclient/tests/unit/v2/cli/test_node.py", line 124, in test_node_list_ansible_inventory
2016-08-16 04:11:15.195753 | rv = self.exec_command(args)
2016-08-16 04:11:15.195811 | File "fuelclient/tests/unit/v2/cli/test_engine.py", line 56, in exec_command
2016-08-16 04:11:15.195847 | return main_mod.main(argv=argv)
2016-08-16 04:11:15.195887 | File "fuelclient/main.py", line 80, in main
2016-08-16 04:11:15.195961 | return fuelclient_app.run(argv)
2016-08-16 04:11:15.196008 | File "fuelclient/main.py", line 71, in run
2016-08-16 04:11:15.196065 | return super(FuelClient, self).run(argv)
2016-08-16 04:11:15.196168 | File "/home/jenkins/workspace/gate-python-fuelclient-python27-ubuntu-xenial/.tox/py27/local/lib/python2.7/site-packages/cliff/app.py", line 267, in run
2016-08-16 04:11:15.196208 | result = self.run_subcommand(remainder)
2016-08-16 04:11:15.196314 | File "/home/jenkins/workspace/gate-python-fuelclient-python27-ubuntu-xenial/.tox/py27/local/lib/python2.7/site-packages/cliff/app.py", line 387, in run_subcommand
2016-08-16 04:11:15.196349 | result = cmd.run(parsed_args)
2016-08-16 04:11:15.196457 | File "/home/jenkins/workspace/gate-python-fuelclient-python27-ubuntu-xenial/.tox/py27/local/lib/python2.7/site-packages/cliff/command.py", line 59, in run
2016-08-16 04:11:15.196495 | return self.take_action(parsed_args) or 0
2016-08-16 04:11:15.196540 | File "fuelclient/commands/node.py", line 501, in take_action
2016-08-16 04:11:15.196584 | self.app.stdout.write(u'[{role}]\n'.format(role=role))
2016-08-16 04:11:15.196665 | File "/home/jenkins/workspace/gate-python-fuelclient-python27-ubuntu-xenial/.tox/py27/lib/python2.7/codecs.py", line 370, in write
2016-08-16 04:11:15.196694 | self.stream.write(data)
2016-08-16 04:11:15.196732 | TypeError: unicode argument expected, got 'str'

Steps to reproduce:
Put any commit to python-fuelclient master.

Reproducibility:
Always

Impact:
 Can be marked as CRITICAL as it blocks workflow