use six.StringIO for compatibility with io.StringIO in python3

The newer version of six (1.4.1) provides six.StringIO which
is a fake file object for textual data. It's an alias for cStringIO.StringIO,
in python2 and io.StringIO in Python3.

Change-Id: If1ccfca128385f976938f0f0c74573687faad9ac
Signed-off-by: Chuck Short <chuck.short@canonical.com>

keystoneclient/tests/test_shell.py

@@ -13,7 +13,6 @@
 #    under the License.
 
 import argparse
-import cStringIO
 import json
 import os
 import sys
@@ -21,6 +20,7 @@ import uuid
 
 import fixtures
 import mock
+import six
 import testtools
 from testtools import matchers
 
@@ -80,7 +80,7 @@ class ShellTest(utils.TestCase):
         clean_env = {}
         _old_env, os.environ = os.environ, clean_env.copy()
         try:
-            sys.stdout = cStringIO.StringIO()
+            sys.stdout = six.StringIO()
             _shell = openstack_shell.OpenStackIdentityShell()
             _shell.main(argstr.split())
         except SystemExit:

keystoneclient/tests/v2_0/test_shell.py

@@ -12,11 +12,11 @@
 #    License for the specific language governing permissions and limitations
 #    under the License.
 
-import cStringIO
 import os
 import sys
 
 from mox3 import stubout
+import six
 from testtools import matchers
 
 from keystoneclient import httpclient
@@ -69,7 +69,7 @@ class ShellTests(utils.TestCase):
     def run_command(self, cmd):
         orig = sys.stdout
         try:
-            sys.stdout = cStringIO.StringIO()
+            sys.stdout = six.StringIO()
             if isinstance(cmd, list):
                 self.shell.main(cmd)
             else: