Fixed some locations to work with autocommit=True

- backends: supports_transactions()
 - select_for_update tests

django/db/backends/__init__.py

@@ -417,6 +417,12 @@ class BaseDatabaseFeatures(object):
     @cached_property
     def supports_transactions(self):
         "Confirm support for transactions"
+        try:
+            # Make sure to run inside a managed transaction block,
+            # otherwise autocommit will cause the confimation to
+            # fail.
+            self.connection.enter_transaction_management()
+            self.connection.managed(True)
             cursor = self.connection.cursor()
             cursor.execute('CREATE TABLE ROLLBACK_TEST (X INT)')
             self.connection._commit()
@@ -426,6 +432,9 @@ class BaseDatabaseFeatures(object):
             count, = cursor.fetchone()
             cursor.execute('DROP TABLE ROLLBACK_TEST')
             self.connection._commit()
+            self.connection._dirty = False
+        finally:
+            self.connection.leave_transaction_management()
         return count == 0
 
     @cached_property

tests/modeltests/select_for_update/tests.py

@@ -36,6 +36,8 @@ class SelectForUpdateTests(TransactionTestCase):
         # issuing a SELECT ... FOR UPDATE will block.
         new_connections = ConnectionHandler(settings.DATABASES)
         self.new_connection = new_connections[DEFAULT_DB_ALIAS]
+        self.new_connection.enter_transaction_management()
+        self.new_connection.managed(True)
 
         # We need to set settings.DEBUG to True so we can capture
         # the output SQL to examine.
@@ -48,6 +50,7 @@ class SelectForUpdateTests(TransactionTestCase):
             # this in the course of their run.
             transaction.managed(False)
             transaction.leave_transaction_management()
+            self.new_connection.leave_transaction_management()
         except transaction.TransactionManagementError:
             pass
         self.new_connection.close()
@@ -66,7 +69,7 @@ class SelectForUpdateTests(TransactionTestCase):
             'for_update': self.new_connection.ops.for_update_sql(),
             }
         self.cursor.execute(sql, ())
-        result = self.cursor.fetchone()
+        self.cursor.fetchone()
 
     def end_blocking_transaction(self):
         # Roll back the blocking transaction.