Replace jsonutils by common json package

This PS is going to following item:

- Remove dependency oslo.serialization which only use at one test-case
  and use build-in python package that is json[1] in the code-base.
- Ignore N521 check in the flake which no longer need to check when we
  change into json.

[1] https://docs.python.org/3.6/library/json.html

Change-Id: I22cf66d1ea5666a072a06456213a7964c5deced8

neutron_fwaas/tests/tempest_plugin/tests/scenario/manager.py

@@ -14,11 +14,11 @@
 #    License for the specific language governing permissions and limitations
 #    under the License.
 
+import json
 import subprocess
 
 import netaddr
 from oslo_log import log
-from oslo_serialization import jsonutils
 from oslo_utils import netutils
 
 from tempest.common import compute
@@ -472,7 +472,7 @@ class ScenarioTest(tempest.test.BaseTestCase):
 
         bdm = image_props.get('block_device_mapping')
         if bdm:
-            bdm = jsonutils.loads(bdm)
+            bdm = json.loads(bdm)
             if bdm and 'snapshot_id' in bdm[0]:
                 snapshot_id = bdm[0]['snapshot_id']
                 self.addCleanup(

requirements.txt

@@ -13,7 +13,6 @@ oslo.config>=5.1.0 # Apache-2.0
 oslo.db>=4.27.0 # Apache-2.0
 oslo.log>=3.30.0 # Apache-2.0
 oslo.messaging>=5.29.0 # Apache-2.0
-oslo.serialization!=2.19.1,>=2.18.0 # Apache-2.0
 oslo.service>=1.24.0 # Apache-2.0
 oslo.utils>=3.31.0 # Apache-2.0
 oslo.privsep>=1.23.0 # Apache-2.0

tox.ini

@@ -94,7 +94,8 @@ commands = python setup.py build_sphinx
 # H106: Do not put vim configuration in source files
 # H203: Use assertIs(Not)None to check for None
 # H904: Delay string interpolations at logging calls
-ignore = E125,E126,E128,E129,E265,H404,H405,N530
+# N521: jsonutils.loads must be used instead of json.loads
+ignore = E125,E126,E128,E129,E265,H404,H405,N530,N521
 enable-extensions=H106,H203,H904
 show-source = true
 exclude = .venv,.git,.tox,dist,doc,*lib/python*,.tmp,*egg,build,tools,.ropeproject,rally-scenarios