Replace six.iteritems() with .items()

1.As mentioned in [1], we should avoid using six.iteritems to
achieve iterators. We can use dict.items instead, as it will
return iterators in PY3 as well. And dict.items/keys will more
readable.
2.In py2, the performance about list should be negligible,
see the link [2].
[1] https://wiki.openstack.org/wiki/Python3
[2] http://lists.openstack.org/pipermail/openstack-dev/2015-June/066391.html

Change-Id: I522e8f06e8a31b0d591db825d0c1608f162cbbc6

freezer/scheduler/freezer_scheduler.py

@@ -25,7 +25,6 @@ from apscheduler.schedulers import background
 from freezerclient.v1 import client
 from oslo_config import cfg
 from oslo_log import log
-import six
 
 from freezer.scheduler import arguments
 from freezer.scheduler import scheduler_job
@@ -181,7 +180,7 @@ class FreezerScheduler(object):
                 job.process_event(job_doc)
 
         # request removal of any job that has been removed in the api
-        for job_id, job in six.iteritems(self.jobs):
+        for job_id, job in self.jobs.items():
             if job_id not in work_job_id_list:
                 job.remove()
 

freezer/tests/integration/common.py

@@ -25,7 +25,7 @@ import tempfile
 import unittest
 
 import paramiko
-import six
+
 from six.moves import range
 
 FREEZERC = distutils.spawn.find_executable('freezer-agent')
@@ -47,7 +47,7 @@ class CommandFailed(Exception):
 
 
 def dict_to_args(d):
-    l = [['--' + k.replace('_', '-'), v] for k, v in six.iteritems(d)]
+    l = [['--' + k.replace('_', '-'), v] for k, v in d.items()]
     return list(itertools.chain.from_iterable(l))
 
 

freezer/utils/winutils.py

@@ -15,7 +15,6 @@
 import ctypes
 import json
 import os
-import six
 import sys
 
 
@@ -75,5 +74,5 @@ def set_environment(home):
     json_env = os.path.join(home, 'env.json')
     with open(json_env, 'rb') as fp:
         env = json.loads(fp.read())
-        for k, v in six.iteritems(env):
+        for k, v in env.items():
             os.environ[str(k).strip()] = str(v).strip()