Return HTTP code 400 when creating an audit with wrong parameters

Currently, when trying to create an audit which misses a mandatory
parameter watcher returns error 500 instead of 400 which is the
documented error in the API [1] and the appropiate error code for
malformed requests.

This patch catch parameters validation errors according to the json
schema for each strategy and returns error 400. It also fixes the
unit test to validate the expected behavior.

[1] https://docs.openstack.org/api-ref/resource-optimization/#audits

Closes-Bug: #2110538
Change-Id: I23232b3b54421839bb01d54386d4e7b244f4e2a0

releasenotes/notes/return-error-400-on-bad-parameters-bb964e4f5cadc15c.yaml

@@ -0,0 +1,7 @@
+---
+fixes:
+  - |
+    `Bug #2110538 <https://bugs.launchpad.net/watcher/+bug/2110538>`_:
+    Corrected the HTTP error code returned when watcher users try to create
+    audits with invalid parameters. The API now correctly returns a 400 Bad
+    Request error.

watcher/api/controllers/v1/audit.py

@@ -33,6 +33,7 @@ import datetime
 from dateutil import tz
 
 from http import HTTPStatus
+import jsonschema
 from oslo_log import log
 from oslo_utils import timeutils
 import pecan
@@ -627,8 +628,12 @@ class AuditsController(rest.RestController):
             if schema:
                 # validate input parameter with default value feedback
                 no_schema = False
-                utils.StrictDefaultValidatingDraft4Validator(schema).validate(
-                    audit.parameters)
+                try:
+                    utils.StrictDefaultValidatingDraft4Validator(
+                        schema).validate(audit.parameters)
+                except jsonschema.exceptions.ValidationError as e:
+                    raise exception.Invalid(
+                        _('Invalid parameters for strategy: %s') % e)
 
         if no_schema and audit.parameters:
             raise exception.Invalid(_('Specify parameters but no predefined '

watcher/tests/api/v1/test_audits.py

@@ -843,16 +843,12 @@ class TestPost(api_base.FunctionalTest):
             del audit_dict[k]
 
         response = self.post_json('/audits', audit_dict, expect_errors=True)
-        # (amoralej) This should return HTTPStatus.BAD_REQUEST, however this
-        # review is adding the test to show wrong code is returned. I will
-        # switch this to be HTTPStatus.BAD_REQUEST in the fixing review.
-        self.assertEqual(HTTPStatus.INTERNAL_SERVER_ERROR, response.status_int)
+        self.assertEqual(HTTPStatus.BAD_REQUEST, response.status_int)
         self.assertEqual("application/json", response.content_type)
-        # (amoralej) uncomment with the fix
-        # expected_error_msg = (
-        #    "Invalid parameters for strategy: 'fake1' is a required property")
-        # self.assertTrue(response.json['error_message'])
-        # self.assertIn(expected_error_msg, response.json['error_message'])
+        expected_error_msg = (
+            "Invalid parameters for strategy: 'fake1' is a required property")
+        self.assertTrue(response.json['error_message'])
+        self.assertIn(expected_error_msg, response.json['error_message'])
         assert not mock_trigger_audit.called
 
     def prepare_audit_template_strategy_with_parameter(self):