Fixed #28498 -- Fixed test database creation with cx_Oracle 6.

tests/select_for_update/tests.py

@@ -56,6 +56,7 @@ class SelectForUpdateTests(TransactionTestCase):
 
     def end_blocking_transaction(self):
         # Roll back the blocking transaction.
+        self.cursor.close()
         self.new_connection.rollback()
         self.new_connection.set_autocommit(True)
 
@@ -370,7 +371,10 @@ class SelectForUpdateTests(TransactionTestCase):
             finally:
                 # This method is run in a separate thread. It uses its own
                 # database connection. Close it without waiting for the GC.
-                connection.close()
+                # Connection cannot be closed on Oracle because cursor is still
+                # open.
+                if connection.vendor != 'oracle':
+                    connection.close()
 
         status = []
         thread = threading.Thread(target=raw, kwargs={'status': status})