Merge lp:~julian-edwards/maas/1.6-savepoints-migration into lp:maas/1.6

[Julian Edwards]

Fix the 0088_z_backport_trunk_0099 migration which gave a transaction error if matching Network records already existed.

[Julian Edwards (julian-edwards)]

Selfie. Already discussed with rvb, and I've tested it by re-running the same migration on a 1.6.1 installed Trusty machine.

review: Approve

=== modified file 'src/maasserver/migrations/0088_z_backport_trunk_0099.py'
--- src/maasserver/migrations/0088_z_backport_trunk_0099.py	2014-08-21 06:06:14 +0000
+++ src/maasserver/migrations/0088_z_backport_trunk_0099.py	2014-08-25 01:49:08 +0000
@@ -1,5 +1,5 @@
 from django.core.exceptions import ValidationError
-from django.db import models
+from django.db import models, transaction
 from django.db.utils import IntegrityError
 from netaddr import IPNetwork
 from south.db import db
@@ -44,10 +44,13 @@
                     "Auto created when creating interface %s on cluster "
                     "%s" % (interface.interface, interface.nodegroup.name)),
                 )
+            sid = transaction.savepoint()
             try:
                 network.save()
+                transaction.savepoint_commit(sid)
             except (ValidationError, IntegrityError):
                 # It probably already exists, keep calm and carry on.
+                transaction.savepoint_rollback(sid)
                 continue
 
     def backwards(self, orm):