Remove warning about session with and without enginefacade

Now we moved all code to the new enginefacade so we don't need this
check anymore.
And BTW. I think it wasn't working properly as even if we are using new
facade we still see plenty of those warnings in e.g. logs of the
neutron functional tests CI job.

Partially-Implements blueprint: enginefacade-switch

Change-Id: Ib2933e4f52e8d7585c13a0d1a3485389fa37b432

neutron_lib/context.py

@@ -15,7 +15,6 @@
 import collections
 import copy
 import datetime
-import warnings
 
 from oslo_config import cfg
 from oslo_context import context as oslo_context
@@ -148,18 +147,17 @@ class Context(ContextBaseWithSession):
 
     @property
     def session(self):
-        # TODO(akamyshnikova): checking for session attribute won't be needed
-        # when reader and writer will be used
+        # TODO(ralonsoh): "Context.session" is provided by
+        # "enginefacade.transaction_context_provider" when a new transaction,
+        # READER or WRITER, is created. This property is just a temporary fix
+        # for those transactions that are not executed inside a transaction.
+        # By manually selecting the type of transaction we can speed up the
+        # code because by default a writer session is always created, even
+        # within read only operations.
         if hasattr(super(), 'session'):
-            if self._session:
-                warnings.warn('context.session is used with and without '
-                              'new enginefacade. Please update the code to '
-                              'use new enginefacede consistently.',
-                              DeprecationWarning)
-            return super().session
+            self._session = super().session
         if self._session is None:
             self._session = db_api.get_writer_session()
-
         return self._session
 
     def set_transaction_constraint(self, resource, resource_id, rev_number):

neutron_lib/db/api.py

@@ -213,7 +213,8 @@ def retry_if_session_inactive(context_var_name='context'):
             context = kwargs.get(context_var_name)
             if context is None:
                 context = args[ctx_arg_index]
-            method = f if context.session.is_active else f_with_retry
+            method = (f if (context.session and context.session.is_active)
+                      else f_with_retry)
             return method(*args, **kwargs)
         return wrapped
     return decorator

neutron_lib/tests/unit/test_context.py

@@ -214,12 +214,6 @@ class TestNeutronContext(_base.BaseTestCase):
         self.assertDictSupersetOf(values, policy_values)
         self.assertDictSupersetOf(additional_values, policy_values)
 
-    @mock.patch.object(context.ContextBaseWithSession, 'session')
-    def test_superclass_session(self, mocked_session):
-        ctx = context.Context('user_id', 'tenant_id')
-        # make sure context uses parent class session that is mocked
-        self.assertEqual(mocked_session, ctx.session)
-
     def test_session_cached(self):
         ctx = context.Context('user_id', 'tenant_id')
         session1 = ctx.session