Use public API from oslo.service

Some of the earlier public apis have been made private
in next oslo.service release.

Change-Id: I0c85ffaa6755a60d37714609d8b95a942b3b7168
Signed-off-by: rabi <ramishra@redhat.com>

heat/engine/service.py

@@ -30,8 +30,8 @@ from oslo_context import context as oslo_context
 from oslo_log import log as logging
 import oslo_messaging as messaging
 from oslo_serialization import jsonutils
-from oslo_service.backend.threading import threadgroup
 from oslo_service import service
+from oslo_service import threadgroup
 from oslo_utils import timeutils
 from oslo_utils import uuidutils
 from osprofiler import profiler

heat/tests/common.py

@@ -11,12 +11,17 @@
 #    License for the specific language governing permissions and limitations
 #    under the License.
 
+# flake8: noqa: E402
+
 import os
 import sys
 
 import fixtures
 from oslo_config import cfg
 from oslo_log import log as logging
+from oslo_service import backend
+backend.init_backend(backend.BackendType.THREADING)
+
 import testscenarios
 import testtools
 

tox.ini

@@ -112,7 +112,8 @@ show-source = true
 # E123 closing bracket does not match indentation of opening bracket's line
 # W503 line break before binary operator
 # W504 line break after binary operator
-ignore = E123,W503,W504
+# TODO(tkajinam): Check why Nnnn checks from neutron-lib are enabled
+ignore = E123,W503,W504,N
 exclude=.*,dist,*lib/python*,*egg,build,*convergence/scenarios/*
 max-complexity=23