Add hacking check for 3rd party mock

Change-Id: I25715d04791e9c8c681a63954719d48f7b390dcd
Signed-off-by: Sean McGinnis <sean.mcginnis@gmail.com>

cinder/tests/hacking/checks.py

@@ -372,3 +372,18 @@ def validate_assertTrue(logical_line, filename):
         msg = ("C313: Unit tests should use assertTrue(value) instead"
                " of using assertEqual(True, value).")
         yield(0, msg)
+
+
+third_party_mock = re.compile("^import.mock")
+from_third_party_mock = re.compile("^from.mock.import")
+
+
+@core.flake8ext
+def no_third_party_mock(logical_line):
+    # We should only use unittest.mock, not the third party mock library that
+    # was needed for py2 support.
+    if (re.match(third_party_mock, logical_line) or
+            re.match(from_third_party_mock, logical_line)):
+        msg = ('C337: Unit tests should use the standard library "mock" '
+               'module, not the third party mock lib.')
+        yield(0, msg)

cinder/tests/unit/test_hacking.py

@@ -293,3 +293,13 @@ class HackingTestCase(test.TestCase):
     def test_no_test_log(self, first, second, third, fourth):
         self.assertEqual(first, len(list(checks.no_test_log(
             "%s('arg')" % second, third, fourth))))
+
+    @ddt.unpack
+    @ddt.data(
+        (1, 'import mock'),
+        (0, 'from unittest import mock'),
+        (1, 'from mock import patch'),
+        (0, 'from unittest.mock import patch'))
+    def test_no_third_party_mock(self, err_count, line):
+        self.assertEqual(err_count, len(list(checks.no_third_party_mock(
+            line))))

cinder/tests/unit/volume/drivers/test_prophetstor_dpl.py

@@ -14,8 +14,8 @@
 
 import errno
 import re
+from unittest import mock
 
-import mock
 from oslo_utils import units
 from six.moves import http_client
 

tox.ini

@@ -213,6 +213,7 @@ extension =
   C312 = checks:no_translate_logs
   C313 = checks:validate_assertTrue
   C336 = checks:dict_constructor_with_list_copy
+  C337 = checks:no_third_party_mock
 paths = ./cinder/tests/hacking
 
 [doc8]