Fixed #24652 -- Disallowed query execution in SimpleTestCase subclasses.

Thanks to Tim and Anssi for the review.

docs/releases/1.9.txt

@@ -505,6 +505,12 @@ Miscellaneous
 * The ``django.contrib.sites.models.Site.domain`` field was changed to be
   :attr:`~django.db.models.Field.unique`.
 
+* In order to enforce test isolation, database queries are not allowed
+  by default in :class:`~django.test.SimpleTestCase` tests anymore. You
+  can disable this behavior by setting the
+  :attr:`~django.test.SimpleTestCase.allow_database_queries` class attribute
+  to ``True`` on your test class.
+
 .. _deprecated-features-1.9:
 
 Features deprecated in 1.9

docs/topics/testing/tools.txt

@@ -606,6 +606,17 @@ features like:
 then you should use :class:`~django.test.TransactionTestCase` or
 :class:`~django.test.TestCase` instead.
 
+.. attribute:: SimpleTestCase.allow_database_queries
+
+    .. versionadded:: 1.9
+
+    :class:`~SimpleTestCase` disallows database queries by default. This
+    helps to avoid executing write queries which will affect other tests
+    since each ``SimpleTestCase`` test isn't run in a transaction. If you
+    aren't concerned about this problem, you can disable this behavior by
+    setting the ``allow_database_queries`` class attribute to ``True`` on
+    your test class.
+
 ``SimpleTestCase`` inherits from ``unittest.TestCase``.
 
 .. warning::