tempest-lib: can't recieve bytes output from ssh under pyhton3

[Andrey Pavlov]

I tried to run tests under python3 and got error from tempest_lib.common.ssh
This error occurs because channel returns binary_type under python3

(0):~/stackforge/ec2-api$ python3 -m subunit.run discover -t ./ ./ec2api/tests/functional/scenario/ | subunit-2to1 | tools/colorizer.py
ec2api.tests.functional.scenario.test_instances.InstancesTest
    test_userdata FAIL

Slowest 1 tests took 120.23 secs:
ec2api.tests.functional.scenario.test_instances.InstancesTest
    test_userdata 120.23

======================================================================
FAIL: ec2api.tests.functional.scenario.test_instances.InstancesTest.test_userdata
----------------------------------------------------------------------
Traceback (most recent call last):
testtools.testresult.real._StringException: pythonlogging:'': {{{
2015-09-13 10:18:29,570 15182 WARNING [tempest_lib.common.ssh] Failed to establish authenticated ssh connection to cirros@172.24.4.34 ([Errno 113] No route to host). Number attempts: 1. Retry after 2 seconds.
2015-09-13 10:18:32,568 15182 WARNING [tempest_lib.common.ssh] Failed to establish authenticated ssh connection to cirros@172.24.4.34 ([Errno 113] No route to host). Number attempts: 2. Retry after 3 seconds.
2015-09-13 10:18:36,953 15182 WARNING [tempest_lib.common.ssh] Failed to establish authenticated ssh connection to cirros@172.24.4.34 ([Errno 111] Connection refused). Number attempts: 3. Retry after 4 seconds.
}}}

Traceback (most recent call last):
  File "/home/apavlov/stackforge/ec2-api/ec2api/tests/functional/scenario/test_instances.py", line 53, in test_userdata
    data = ssh_client.exec_command('curl %s/latest/user-data' % url)
  File "/usr/local/lib/python3.4/dist-packages/tempest_lib/common/ssh.py", line 147, in exec_command
    return ''.join(out_data)
TypeError: sequence item 0: expected str instance, bytes found

Ran 1 test in 121.986s

FAILED (failures=1)

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/222901
Committed: https://git.openstack.org/cgit/openstack/tempest-lib/commit/?id=083f56ddc974beab4cd51e04ce25d38990151dad
Submitter: Jenkins
Branch: master

commit 083f56ddc974beab4cd51e04ce25d38990151dad
Author: Andrey Pavlov <email address hidden>
Date: Sun Sep 13 10:50:06 2015 +0300

    python3: converts binary data from channel

    paramiko returns chunk of binary type.
    So code must join all chunks with binary type and not as str.
    Also this patchset adds one more parameter 'encoding' for exec
    function to decode binary result to str.

    Closes-Bug: #1495181
    Change-Id: I886c9d0c143d3553876ece7b6d1ac2df7e49d701