Add framework for watcher-status upgrade check

This commit adds the functionality of watcher-status CLI for performing
upgrade checks as part of the Stein cycle upgrade-checkers goal.
It only includes a sample check which must be replaced by real checks in
future.

Change-Id: Ic3d066af439797d6f705e805334f729b52ce3aac
Story: 2003657
Task: 26164

watcher/cmd/status.py

@@ -0,0 +1,53 @@
+# Copyright (c) 2018 NEC, Corp.
+#
+#    Licensed under the Apache License, Version 2.0 (the "License"); you may
+#    not use this file except in compliance with the License. You may obtain
+#    a copy of the License at
+#
+#         http://www.apache.org/licenses/LICENSE-2.0
+#
+#    Unless required by applicable law or agreed to in writing, software
+#    distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+#    WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+#    License for the specific language governing permissions and limitations
+#    under the License.
+
+import sys
+
+from oslo_upgradecheck import upgradecheck
+
+from watcher._i18n import _
+from watcher import conf
+
+CONF = conf.CONF
+
+
+class Checks(upgradecheck.UpgradeCommands):
+
+    """Contains upgrade checks
+
+    Various upgrade checks should be added as separate methods in this class
+    and added to _upgrade_checks tuple.
+    """
+
+    def _sample_check(self):
+        """This is sample check added to test the upgrade check framework
+
+        It needs to be removed after adding any real upgrade check
+        """
+        return upgradecheck.Result(upgradecheck.Code.SUCCESS, 'Sample detail')
+
+    _upgrade_checks = (
+        # Sample check added for now.
+        # Whereas in future real checks must be added here in tuple
+        (_('Sample Check'), _sample_check),
+    )
+
+
+def main():
+    return upgradecheck.main(
+        CONF, project='watcher', upgrade_command=Checks())
+
+
+if __name__ == '__main__':
+    sys.exit(main())