Fixed #21134 -- Prevented queries in broken transactions.

Squashed commit of the following:

commit 63ddb271a44df389b2c302e421fc17b7f0529755
Author: Aymeric Augustin <aymeric.augustin@m4x.org>
Date:   Sun Sep 29 22:51:00 2013 +0200

    Clarified interactions between atomic and exceptions.

commit 2899ec299228217c876ba3aa4024e523a41c8504
Author: Aymeric Augustin <aymeric.augustin@m4x.org>
Date:   Sun Sep 22 22:45:32 2013 +0200

    Fixed TransactionManagementError in tests.

    Previous commit introduced an additional check to prevent running
    queries in transactions that will be rolled back, which triggered a few
    failures in the tests. In practice using transaction.atomic instead of
    the low-level savepoint APIs was enough to fix the problems.

commit 4a639b059ea80aeb78f7f160a7d4b9f609b9c238
Author: Aymeric Augustin <aymeric.augustin@m4x.org>
Date:   Tue Sep 24 22:24:17 2013 +0200

    Allowed nesting constraint_checks_disabled inside atomic.

    Since MySQL handles transactions loosely, this isn't a problem.

commit 2a4ab1cb6e83391ff7e25d08479e230ca564bfef
Author: Aymeric Augustin <aymeric.augustin@m4x.org>
Date:   Sat Sep 21 18:43:12 2013 +0200

    Prevented running queries in transactions that will be rolled back.

    This avoids a counter-intuitive behavior in an edge case on databases
    with non-atomic transaction semantics.

    It prevents using savepoint_rollback() inside an atomic block without
    calling set_rollback(False) first, which is backwards-incompatible in
    tests.

    Refs #21134.

commit 8e3db393853c7ac64a445b66e57f3620a3fde7b0
Author: Aymeric Augustin <aymeric.augustin@m4x.org>
Date:   Sun Sep 22 22:14:17 2013 +0200

    Replaced manual savepoints by atomic blocks.

    This ensures the rollback flag is handled consistently in internal APIs.

1 files changed, 11 insertions, 6 deletions

diff --git a/tests/force_insert_update/tests.py b/tests/force_insert_update/tests.py
index 706a099872..6d87151d83 100644
--- a/tests/force_insert_update/tests.py
+++ b/tests/force_insert_update/tests.py
@@ -21,24 +21,29 @@ class ForceTests(TestCase):
         # Won't work because force_update and force_insert are mutually
         # exclusive
         c.value = 4
-        self.assertRaises(ValueError, c.save, force_insert=True, force_update=True)
+        with self.assertRaises(ValueError):
+            c.save(force_insert=True, force_update=True)
 
         # Try to update something that doesn't have a primary key in the first
         # place.
         c1 = Counter(name="two", value=2)
-        self.assertRaises(ValueError, c1.save, force_update=True)
+        with self.assertRaises(ValueError):
+            with transaction.atomic():
+                c1.save(force_update=True)
         c1.save(force_insert=True)
 
         # Won't work because we can't insert a pk of the same value.
-        sid = transaction.savepoint()
         c.value = 5
-        self.assertRaises(IntegrityError, c.save, force_insert=True)
-        transaction.savepoint_rollback(sid)
+        with self.assertRaises(IntegrityError):
+            with transaction.atomic():
+                c.save(force_insert=True)
 
         # Trying to update should still fail, even with manual primary keys, if
         # the data isn't in the database already.
         obj = WithCustomPK(name=1, value=1)
-        self.assertRaises(DatabaseError, obj.save, force_update=True)
+        with self.assertRaises(DatabaseError):
+            with transaction.atomic():
+                obj.save(force_update=True)
 
 
 class InheritanceTests(TestCase):