Marked some tests as expected failures on Oracle/cx_Oracle<=5.1.3/Python3

Refs #23843 which is really a cx_Oracle bug

tests/annotations/tests.py

@@ -14,6 +14,25 @@ from django.utils import six
 from .models import Author, Book, Store, DepartmentStore, Company, Employee
 
 
+def cxOracle_513_py3_bug(func):
+    """
+    cx_Oracle versions up to and including 5.1.3 have a bug with respect to
+    string handling under Python3 (essentially, they treat Python3 strings
+    as Python2 strings rather than unicode). This makes some tests here
+    fail under Python 3 -- so we mark them as expected failures.
+
+    See  https://code.djangoproject.com/ticket/23843, in particular comment 6,
+    which points to https://bitbucket.org/anthony_tuininga/cx_oracle/issue/6/
+    """
+    from unittest import expectedFailure
+    from django.db import connection
+
+    if connection.vendor == 'oracle' and six.PY3 and connection.Database.version <= '5.1.3':
+        return expectedFailure(func)
+    else:
+        return func
+
+
 class NonAggregateAnnotationTestCase(TestCase):
     fixtures = ["annotations.json"]
 
@@ -230,6 +249,7 @@ class NonAggregateAnnotationTestCase(TestCase):
                 e.id, e.first_name, e.manager, e.random_value, e.last_name, e.age,
                 e.salary, e.store.name, e.annotated_value))
 
+    @cxOracle_513_py3_bug
     def test_custom_functions(self):
         Company(name='Apple', motto=None, ticker_name='APPL', description='Beautiful Devices').save()
         Company(name='Django Software Foundation', motto=None, ticker_name=None, description=None).save()
@@ -255,6 +275,7 @@ class NonAggregateAnnotationTestCase(TestCase):
             lambda c: (c.name, c.tagline)
         )
 
+    @cxOracle_513_py3_bug
     def test_custom_functions_can_ref_other_functions(self):
         Company(name='Apple', motto=None, ticker_name='APPL', description='Beautiful Devices').save()
         Company(name='Django Software Foundation', motto=None, ticker_name=None, description=None).save()