Python3: Replace dict.iteritems with six.iteritems

This also adds a check to nova/hacking/checks.py that
should check dict.iteritems, dict.itervalues and
dict.iterkeys should not be used in the future.

NOTE:
In _dict_from_object() method of test_db_api.py items() method
is called on dict and iteritems() method is called if object is
other than dict. Changed it to directly use obj.items as obj can
either be dict or object of nova.db.sqlalchemy.models.<Class> and
both have items() method.

Partially-Implements: blueprint nova-python3-mitaka

Change-Id: Ib0fe3066199b92e4f013bb15312ada7515fa3d7b

HACKING.rst

@@ -54,6 +54,9 @@ Nova Specific Commandments
 - [N341] contextlib.nested is deprecated
 - [N342] Config options should be in the central location ``nova/conf/``
 - [N343] Check for common double word typos
+- [N344] Python 3: do not use dict.iteritems.
+- [N345] Python 3: do not use dict.iterkeys.
+- [N346] Python 3: do not use dict.itervalues.
 
 Creating Unit Tests
 -------------------

nova/hacking/checks.py

@@ -591,6 +591,27 @@ def check_doubled_words(physical_line, filename):
         return (0, msg % {'word': match.group(1)})
 
 
+def check_python3_no_iteritems(logical_line):
+    msg = ("N344: Use six.iteritems() instead of dict.iteritems().")
+
+    if re.search(r".*\.iteritems\(\)", logical_line):
+        yield(0, msg)
+
+
+def check_python3_no_iterkeys(logical_line):
+    msg = ("N345: Use six.iterkeys() instead of dict.iterkeys().")
+
+    if re.search(r".*\.iterkeys\(\)", logical_line):
+        yield(0, msg)
+
+
+def check_python3_no_itervalues(logical_line):
+    msg = ("N346: Use six.itervalues() instead of dict.itervalues().")
+
+    if re.search(r".*\.itervalues\(\)", logical_line):
+        yield(0, msg)
+
+
 def factory(register):
     register(import_no_db_in_virt)
     register(no_db_session_in_public_api)
@@ -621,3 +642,6 @@ def factory(register):
     register(check_greenthread_spawns)
     register(check_config_option_in_central_place)
     register(check_doubled_words)
+    register(check_python3_no_iteritems)
+    register(check_python3_no_iterkeys)
+    register(check_python3_no_itervalues)

nova/tests/unit/db/test_db_api.py

@@ -1520,11 +1520,8 @@ class ModelsObjectComparatorMixin(object):
     def _dict_from_object(self, obj, ignored_keys):
         if ignored_keys is None:
             ignored_keys = []
-        if isinstance(obj, dict):
-            obj_items = obj.items()
-        else:
-            obj_items = obj.iteritems()
-        return {k: v for k, v in obj_items
+
+        return {k: v for k, v in obj.items()
                 if k not in ignored_keys}
 
     def _assertEqualObjects(self, obj1, obj2, ignored_keys=None):
@@ -7385,7 +7382,7 @@ class ComputeNodeTestCase(test.TestCase, ModelsObjectComparatorMixin):
         service_data['host'] = 'host2'
         service = db.service_create(self.ctxt, service_data)
 
-        existing_node = dict(self.item.iteritems())
+        existing_node = dict(self.item.items())
         expected = [existing_node]
 
         for name in ['bm_node1', 'bm_node2']:

nova/tests/unit/test_hacking.py

@@ -639,3 +639,24 @@ class HackingTestCase(test.NoDBTestCase):
 
         code = "This is the then best comment"
         self._assert_has_no_errors(code, checks.check_doubled_words)
+
+    def test_dict_iteritems(self):
+        self.assertEqual(1, len(list(checks.check_python3_no_iteritems(
+            "obj.iteritems()"))))
+
+        self.assertEqual(0, len(list(checks.check_python3_no_iteritems(
+            "six.iteritems(ob))"))))
+
+    def test_dict_iterkeys(self):
+        self.assertEqual(1, len(list(checks.check_python3_no_iterkeys(
+            "obj.iterkeys()"))))
+
+        self.assertEqual(0, len(list(checks.check_python3_no_iterkeys(
+            "six.iterkeys(ob))"))))
+
+    def test_dict_itervalues(self):
+        self.assertEqual(1, len(list(checks.check_python3_no_itervalues(
+            "obj.itervalues()"))))
+
+        self.assertEqual(0, len(list(checks.check_python3_no_itervalues(
+            "six.itervalues(ob))"))))