hacking: Always use 'assertIs(Not)None'

This is per the OpenStack style guidelines.

Change-Id: Ia706045fe3524b6b5e1db0140672776d481a0c01

HACKING.rst

@@ -26,8 +26,8 @@ Nova Specific Commandments
   assertIsInstance(A, B).
 - [N317] Change assertEqual(type(A), B) by optimal assert like
   assertIsInstance(A, B)
-- [N318] Change assertEqual(A, None) or assertEqual(None, A) by optimal assert like
-  assertIsNone(A)
+- [N318] Change assertEqual(A, None) or assertIs(A, None) to optimal assert
+  like assertIsNone(A)
 - [N319] Validate that debug level logs are not translated.
 - [N320] Setting CONF.* attributes directly in tests is forbidden. Use
   self.flags(option=value) instead.

nova/hacking/checks.py

@@ -58,10 +58,6 @@ asse_equal_in_end_with_true_or_false_re = re.compile(r"assertEqual\("
                     r"(\w|[][.'\"])+ in (\w|[][.'\", ])+, (True|False)\)")
 asse_equal_in_start_with_true_or_false_re = re.compile(r"assertEqual\("
                     r"(True|False), (\w|[][.'\"])+ in (\w|[][.'\", ])+\)")
-asse_equal_end_with_none_re = re.compile(
-                           r"assertEqual\(.*?,\s+None\)$")
-asse_equal_start_with_none_re = re.compile(
-                           r"assertEqual\(None,")
 # NOTE(snikitin): Next two regexes weren't united to one for more readability.
 #                 asse_true_false_with_in_or_not_in regex checks
 #                 assertTrue/False(A in B) cases where B argument has no spaces
@@ -283,11 +279,20 @@ def assert_equal_none(logical_line):
 
     N318
     """
-    res = (asse_equal_start_with_none_re.search(logical_line) or
-           asse_equal_end_with_none_re.search(logical_line))
-    if res:
+    _start_re = re.compile(r"assertEqual\(.*?,\s+None\)$")
+    _end_re = re.compile(r"assertEqual\(None,")
+
+    if _start_re.search(logical_line) or _end_re.search(logical_line):
         yield (0, "N318: assertEqual(A, None) or assertEqual(None, A) "
-               "sentences not allowed")
+               "sentences not allowed. Use assertIsNone(A) instead.")
+
+    _start_re = re.compile(r"assertIs(Not)?\(None,")
+    _end_re = re.compile(r"assertIs(Not)?\(.*,\s+None\)$")
+
+    if _start_re.search(logical_line) or _end_re.search(logical_line):
+        yield (0, "N318: assertIsNot(A, None) or assertIsNot(None, A) must "
+               "not be used. Use assertIsNone(A) or assertIsNotNone(A) "
+               "instead.")
 
 
 def check_python3_xrange(logical_line):

nova/tests/unit/test_hacking.py

@@ -168,9 +168,19 @@ class HackingTestCase(test.NoDBTestCase):
         self.assertEqual(
             len(list(checks.assert_equal_none("self.assertIsNone()"))), 0)
 
-    def test_assert_true_or_false_with_in_or_not_in(self):
         self.assertEqual(len(list(checks.assert_equal_none(
-            "self.assertEqual(A, None)"))), 1)
+            "self.assertIs(A, None)"))), 1)
+
+        self.assertEqual(len(list(checks.assert_equal_none(
+            "self.assertIsNot(A, None)"))), 1)
+
+        self.assertEqual(len(list(checks.assert_equal_none(
+            "self.assertIs(None, A)"))), 1)
+
+        self.assertEqual(len(list(checks.assert_equal_none(
+            "self.assertIsNot(None, A)"))), 1)
+
+    def test_assert_true_or_false_with_in_or_not_in(self):
         self.assertEqual(len(list(checks.assert_true_or_false_with_in(
             "self.assertTrue(A in B)"))), 1)