ERP5Type: make sure we can use mock in tests

In ERP5 software release we now have `mock` egg installed, so we can use it in tests instead of doing manually like this:

```python
saved_method = Class.method
def patched_method():
  ...
try:
   Class.method = patched_method
   ...
finally:
   Class.method = saved_method
```

/reviewed-on nexedi/erp5!882

product/ERP5Type/tests/testERP5Type.py

@@ -32,6 +32,7 @@ except ImportError: # BBB: ZODB < 4
   import cPickle
 import unittest
 import sys
+import mock
 
 import transaction
 from random import randint
@@ -3022,6 +3023,25 @@ return True''')
       self.assertNotEquals(None, method)
       self.assertTrue(method())
 
+    def test_dynamic_accessor_mockable(self):
+      """Test dynamic accessors also work with mock and that
+      generally mock is usable in erp5 tests.
+      """
+      self._addProperty(
+          'Credit Card',
+          self.id(),
+          'test_mocked_property',
+          elementary_type='string',
+          portal_type='Standard Property')
+      doc = self.portal.person_module.newContent(
+          portal_type='Person',
+      ).newContent(
+          portal_type='Credit Card',
+          test_mocked_property='original')
+      with mock.patch('erp5.portal_type.Credit Card.getTestMockedProperty', return_value='mocked'):
+        self.assertEqual('mocked', doc.getTestMockedProperty())
+      self.assertEqual('original', doc.getTestMockedProperty())
+
     def test_type_provider(self):
       self.portal.newContent(id='dummy_type_provider', portal_type="Types Tool")