Replace simplejson by built-in json

Recent python 3 versions provide the built-in json module which meets
the generic requirements. Replace the 3rd party library (simplejson)
by the built-in one to reduce external dependencies.

Change-Id: Id5eccad660be353843f95acfa691d61888983dab

osc_placement/http.py

@@ -11,11 +11,11 @@
 # under the License.
 
 import contextlib
+import json
 import logging
 
 import keystoneauth1.exceptions.http as ks_exceptions
 import osc_lib.exceptions as exceptions
-import simplejson as json
 
 from osc_placement import version
 

osc_placement/tests/functional/base.py

@@ -11,6 +11,7 @@
 # under the License.
 
 import io
+import json
 import logging
 import random
 
@@ -20,7 +21,6 @@ from openstackclient import shell
 from oslotest import base
 from placement.tests.functional.fixtures import capture
 from placement.tests.functional.fixtures import placement
-import simplejson as json
 
 
 # A list of logger names that will be reset to a log level

osc_placement/tests/unit/test_http.py

@@ -10,13 +10,13 @@
 # License for the specific language governing permissions and limitations
 # under the License.
 
+import json
 from unittest import mock
 
 import keystoneauth1.exceptions.http as ks_exceptions
 import osc_lib.exceptions as exceptions
 import oslotest.base as base
 import requests
-import simplejson as json
 
 from osc_placement import http
 from osc_placement import version

requirements.txt

@@ -1,5 +1,4 @@
 pbr>=2.0.0 # Apache-2.0
 keystoneauth1>=3.3.0 # Apache-2.0
-simplejson>=3.16.0 # MIT
 osc-lib>=1.2.0  # Apache-2.0
 oslo.utils>=3.37.0 # Apache-2.0