Py3: Finish the python3 port

- Use six.StringIO instead of StringIO [1].
- Use six.int2byte instead of chr [1].
[1] https://pythonhosted.org/six/

Change-Id: I28d9ce6a435af1f9213c50569d2addf89c722ae3
Closes-bug: #1709546

tempest/api/object_storage/test_account_services.py

@@ -43,7 +43,7 @@ class AccountTest(base.BaseObjectTest):
     def resource_setup(cls):
         super(AccountTest, cls).resource_setup()
         for i in range(ord('a'), ord('f') + 1):
-            name = data_utils.rand_name(name='%s-' % chr(i))
+            name = data_utils.rand_name(name='%s-' % six.int2byte(i))
             cls.container_client.create_container(name)
             cls.containers.append(name)
         cls.containers_count = len(cls.containers)

tempest/tests/lib/test_ssh.py

@@ -12,11 +12,11 @@
 #    License for the specific language governing permissions and limitations
 #    under the License.
 
-from io import StringIO
 import socket
 
 import mock
 import six
+from six import StringIO
 import testtools
 
 from tempest.lib.common import ssh