[goal] Deprecate the JSON formatted policy file

As per the community goal of migrating the policy file
the format from JSON to YAML[1], we need to do two things:

1. Change the default value of '[oslo_policy] policy_file''
config option from 'policy.json' to 'policy.yaml' with
upgrade checks.

2. Deprecate the JSON formatted policy file on the project side
via warning in doc and releasenotes.

Also replace policy.json to policy.yaml ref from doc and tests.

[1]https://governance.openstack.org/tc/goals/selected/wallaby/migrate-policy-format-from-json-to-yaml.html

Change-Id: I207c02ba71fe60635fd3406c9c9364c11f259bae

watcher/cmd/status.py

@@ -14,6 +14,7 @@
 
 import sys
 
+from oslo_upgradecheck import common_checks
 from oslo_upgradecheck import upgradecheck
 
 from watcher._i18n import _
@@ -43,6 +44,10 @@ class Checks(upgradecheck.UpgradeCommands):
     _upgrade_checks = (
         # Added in Train.
         (_('Minimum Nova API Version'), _minimum_nova_api_version),
+        # Added in Wallaby.
+        (_("Policy File JSON to YAML Migration"),
+         (common_checks.check_policy_json, {'conf': CONF})),
+
     )
 
 

watcher/common/policy.py

@@ -18,6 +18,7 @@
 import sys
 
 from oslo_config import cfg
+from oslo_policy import opts
 from oslo_policy import policy
 
 from watcher.common import exception
@@ -26,6 +27,12 @@ from watcher.common import policies
 _ENFORCER = None
 CONF = cfg.CONF
 
+# TODO(gmann): Remove setting the default value of config policy_file
+# once oslo_policy change the default value to 'policy.yaml'.
+# https://github.com/openstack/oslo.policy/blob/a626ad12fe5a3abd49d70e3e5b95589d279ab578/oslo_policy/opts.py#L49
+DEFAULT_POLICY_FILE = 'policy.yaml'
+opts.set_defaults(CONF, DEFAULT_POLICY_FILE)
+
 
 # we can get a policy enforcer by this init.
 # oslo policy support change policy rule dynamically.

watcher/tests/policy_fixture.py

@@ -30,7 +30,7 @@ class PolicyFixture(fixtures.Fixture):
     def _setUp(self):
         self.policy_dir = self.useFixture(fixtures.TempDir())
         self.policy_file_name = os.path.join(self.policy_dir.path,
-                                             'policy.json')
+                                             'policy.yaml')
         with open(self.policy_file_name, 'w') as policy_file:
             policy_file.write(fake_policy.policy_data)
         policy_opts.set_defaults(CONF)