use HTTPStatus instead of direct code

Python introduced http.HTTPStatus since version 3.5,
and Wallaby has targeted a minimum version of python 3.6.

Change-Id: I45f732f0f59b8fae831bb6c07f4fdd98cdd7409a

watcher/api/controllers/v1/action.py

@@ -57,6 +57,7 @@ are dynamically loaded by Watcher at launch time.
 
 import datetime
 
+from http import HTTPStatus
 import pecan
 from pecan import rest
 import wsme
@@ -362,7 +363,7 @@ class ActionsController(rest.RestController):
 
         return Action.convert_with_links(action)
 
-    @wsme_pecan.wsexpose(Action, body=Action, status_code=201)
+    @wsme_pecan.wsexpose(Action, body=Action, status_code=HTTPStatus.CREATED)
     def post(self, action):
         """Create a new action(forbidden).
 
@@ -422,7 +423,7 @@ class ActionsController(rest.RestController):
         action_to_update.save()
         return Action.convert_with_links(action_to_update)
 
-    @wsme_pecan.wsexpose(None, types.uuid, status_code=204)
+    @wsme_pecan.wsexpose(None, types.uuid, status_code=HTTPStatus.NO_CONTENT)
     def delete(self, action_uuid):
         """Delete a action(forbidden).
 

watcher/api/controllers/v1/action_plan.py

@@ -56,6 +56,7 @@ state machine <action_plan_state_machine>`.
 
 import datetime
 
+from http import HTTPStatus
 from oslo_log import log
 import pecan
 from pecan import rest
@@ -460,7 +461,7 @@ class ActionPlansController(rest.RestController):
 
         return ActionPlan.convert_with_links(action_plan)
 
-    @wsme_pecan.wsexpose(None, types.uuid, status_code=204)
+    @wsme_pecan.wsexpose(None, types.uuid, status_code=HTTPStatus.NO_CONTENT)
     def delete(self, action_plan_uuid):
         """Delete an action plan.
 

watcher/api/controllers/v1/audit.py

@@ -32,6 +32,7 @@ states, visit :ref:`the Audit State machine <audit_state_machine>`.
 import datetime
 from dateutil import tz
 
+from http import HTTPStatus
 import pecan
 from pecan import rest
 import wsme
@@ -595,7 +596,8 @@ class AuditsController(rest.RestController):
 
         return Audit.convert_with_links(rpc_audit)
 
-    @wsme_pecan.wsexpose(Audit, body=AuditPostType, status_code=201)
+    @wsme_pecan.wsexpose(Audit, body=AuditPostType,
+                         status_code=HTTPStatus.CREATED)
     def post(self, audit_p):
         """Create a new audit.
 
@@ -717,7 +719,7 @@ class AuditsController(rest.RestController):
         audit_to_update.save()
         return Audit.convert_with_links(audit_to_update)
 
-    @wsme_pecan.wsexpose(None, wtypes.text, status_code=204)
+    @wsme_pecan.wsexpose(None, wtypes.text, status_code=HTTPStatus.NO_CONTENT)
     def delete(self, audit):
         """Delete an audit.
 

watcher/api/controllers/v1/audit_template.py

@@ -45,6 +45,7 @@ will be launched automatically or will need a manual confirmation from the
 
 import datetime
 
+from http import HTTPStatus
 import pecan
 from pecan import rest
 import wsme
@@ -618,7 +619,7 @@ class AuditTemplatesController(rest.RestController):
 
     @wsme.validate(types.uuid, AuditTemplatePostType)
     @wsme_pecan.wsexpose(AuditTemplate, body=AuditTemplatePostType,
-                         status_code=201)
+                         status_code=HTTPStatus.CREATED)
     def post(self, audit_template_postdata):
         """Create a new audit template.
 
@@ -694,7 +695,7 @@ class AuditTemplatesController(rest.RestController):
         audit_template_to_update.save()
         return AuditTemplate.convert_with_links(audit_template_to_update)
 
-    @wsme_pecan.wsexpose(None, wtypes.text, status_code=204)
+    @wsme_pecan.wsexpose(None, wtypes.text, status_code=HTTPStatus.NO_CONTENT)
     def delete(self, audit_template):
         """Delete a audit template.
 

watcher/api/controllers/v1/webhooks.py

@@ -14,6 +14,7 @@
 Webhook endpoint for Watcher v1 REST API.
 """
 
+from http import HTTPStatus
 from oslo_log import log
 import pecan
 from pecan import rest
@@ -36,7 +37,7 @@ class WebhookController(rest.RestController):
         self.dc_client = rpcapi.DecisionEngineAPI()
 
     @wsme_pecan.wsexpose(None, wtypes.text, body=types.jsontype,
-                         status_code=202)
+                         status_code=HTTPStatus.ACCEPTED)
     def post(self, audit_ident, body):
         """Trigger the given audit.
 

watcher/api/hooks.py

@@ -15,7 +15,7 @@
 # under the License.
 
 
-from http import client as http_client
+from http import HTTPStatus
 from oslo_config import cfg
 from pecan import hooks
 
@@ -91,8 +91,8 @@ class NoExceptionTracebackHook(hooks.PecanHook):
         # Do nothing if there is no error.
         # Status codes in the range 200 (OK) to 399 (400 = BAD_REQUEST) are not
         # an error.
-        if (http_client.OK <= state.response.status_int <
-                http_client.BAD_REQUEST):
+        if (HTTPStatus.OK <= state.response.status_int <
+                HTTPStatus.BAD_REQUEST):
             return
 
         json_body = state.response.json