nova-manage: Deprecate 'log' commands

These aren't maintained and their usefulness is questionable, given the
availability of logs in '/var/log/' and the plethora of powerful tools
(Logstash) that can be used to parse these logs in large deployments.

Change-Id: I685512a17b8aea700fadf167571f37ecf1874861

doc/source/man/nova-manage.rst

@@ -183,6 +183,10 @@ Nova Cells v2
 Nova Logs
 ~~~~~~~~~
 
+.. deprecated:: 16.0.0
+
+    This will be removed in 17.0.0 (Queens)
+
 ``nova-manage logs errors``
 
     Displays nova errors from log files.

nova/cmd/manage.py

@@ -959,6 +959,11 @@ class AgentBuildCommands(object):
 class GetLogCommands(object):
     """Get logging information."""
 
+    # TODO(stephenfin): Remove this during the Queens cycle
+    description = ('DEPRECATED: The log commands are deprecated since '
+                   'Pike as they are not maintained. They will be removed '
+                   'in an upcoming release.')
+
     def errors(self):
         """Get all of the errors from the log files."""
         error_found = 0

releasenotes/notes/deprecate-nova-manage-commands-9de1abbc94e06d16.yaml

@@ -30,6 +30,13 @@ deprecations:
       This allows for the listing of compute hosts. Operators should use the
       equivalent resources in the `REST API`__ instead.
 
+    `log`
+
+      This allows for the filtering of errors from nova's logs and extraction
+      of all logs from syslog. This command has not been actively maintained in
+      a long time, is not tested, and can be achieved using `journalctl` or by
+      simply grepping through ``/var/log``. It will simply be removed.
+
     `project`
 
       This is an alias for `account` and has been deprecated for the same