nova-manage: Deprecate 'shell' commands

The usefulness of these options is dubious at best and there's no real
reason to keep them around. Deprecate this command now, with the plan to
remove it entirely in Queens.

Change-Id: I5c578d4f322cab1be69b8e498a8dd3bbff29b269
Partially-Implements: bp move-nova-cmds-to-cliff

doc/source/man/nova-manage.rst

@@ -192,6 +192,10 @@ Nova Logs
 Nova Shell
 ~~~~~~~~~~
 
+.. deprecated:: 16.0.0
+
+    This will be removed in 17.0.0 (Queens)
+
 ``nova-manage shell bpython``
 
     Starts a new bpython shell.

nova/cmd/manage.py

@@ -118,6 +118,12 @@ def param2id(object_id):
 
 
 class ShellCommands(object):
+
+    # TODO(stephenfin): Remove this during the Queens cycle
+    description = ('DEPRECATED: The shell commands are deprecated since '
+                   'Pike as they serve no useful purpose in modern nova. '
+                   'They will be removed in an upcoming release.')
+
     def bpython(self):
         """Runs a bpython shell.
 

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

@@ -0,0 +1,14 @@
+---
+deprecations:
+  - |
+    A number of `nova-manage` commands have been deprecated. The commands,
+    along with the reasons for their deprecation, are listed below:
+
+    `shell`
+
+      This starts the Python interactive interpreter. It is a clone of the same
+      functionality found in Django's `django-manage` command. This command
+      hasn't been actively maintained in a long time and is not tested. It will
+      simply be removed.
+
+    These commands will be removed in their entirety during the Queens cycle.