Tested that get_or_create raises IntegrityError.

It used to raise "DatabaseError: no such savepoint" with the old
transaction management. Closes #15117.

tests/get_or_create/models.py

@@ -24,3 +24,7 @@ class Person(models.Model):
 class ManualPrimaryKeyTest(models.Model):
     id = models.IntegerField(primary_key=True)
     data = models.CharField(max_length=100)
+
+
+class Profile(models.Model):
+    person = models.ForeignKey(Person, primary_key=True)