Folder: fix checkConsistency on folder containing non erp5 objects

contentValues() nowadays return also non ERP5-ish objects such as python
scripts , OFS.File etc. Because of that, if an ERP5 Folder contained a
non ERP5 object, which does not have fixConsistency or checkConsistency
methods, Folder.checkConsistency was causing an infinite loop because it
was acquiring checkConsistency method from self.

bt5/erp5_core_test/TestTemplateItem/portal_components/test.erp5.testConstraint.py

@@ -1616,6 +1616,32 @@ class TestConstraint(PropertySheetTestCase):
     document.checkConsistency()
     self.assertEqual("Fooa", document.getTitle())
 
+  def test_checkConsistency_is_recursive(self):
+    self._addProperty(
+        self.object_content_portal_type,
+        self.id(),
+        commit=True,
+        property_id="title_constraint",
+        portal_type='Attribute Equality Constraint',
+        constraint_attribute_name = 'title',
+        constraint_attribute_value = 'string:a',
+    )
+
+    obj = self._makeOne()
+    self.assertEqual([], obj.checkConsistency())
+    self.assertEqual([], obj.fixConsistency())
+
+    obj.newContent(portal_type=self.object_content_portal_type)
+    self.assertEqual(1, len(obj.checkConsistency()))
+    self.assertEqual(1, len(obj.fixConsistency()))
+
+    # non ERP5 objects are ignored
+    from OFS.Image import manage_addFile
+    manage_addFile(obj, self.id(),)
+    self.assertEqual(1, len(obj.checkConsistency()))
+    self.assertEqual(1, len(obj.fixConsistency()))
+
+
 def test_suite():
   suite = unittest.TestSuite()
   suite.addTest(unittest.makeSuite(TestConstraint))

product/ERP5Type/Core/Folder.py

@@ -1465,11 +1465,11 @@ class Folder(FolderMixIn, CopyContainer, ObjectManager, Base, OFSFolder2, CMFBTr
         # of this name implement consistency checking on object
         continue
       if fixit:
-        extra_errors = obj.fixConsistency(filter=filter, **kw)
+        if hasattr(aq_base(obj), 'fixConsistency'):
+          error_list.extend(obj.fixConsistency(filter=filter, **kw))
       else:
-        extra_errors = obj.checkConsistency(filter=filter, **kw)
-      if len(extra_errors) > 0:
-        error_list += extra_errors
+        if hasattr(aq_base(obj), 'checkConsistency'):
+          error_list.extend(obj.checkConsistency(filter=filter, **kw))
     # We should also return an error if any
     return error_list