Deprecating commands

There are times when commands need to be deprecated due to rename or removal. The process for command deprecation is:

1. Push up a change for review which deprecates the command(s).

   • The change should print a deprecation warning to stderr each time a deprecated command is used.

   • That warning message should include a rough timeline for when the command will be removed and what should be used instead, if anything.

   • The description in the help text for the deprecated command should mark that it is deprecated.

   • The change should include a release note with the deprecations section filled out.

   • The deprecation cycle is typically the first client release after the next full nova server release so that there is at least six months of deprecation.

2. Once the change is approved, have a member of the nova-release team release a new version of python-novaclient.

3. Example: https://review.opendev.org/#/c/185141/

   This change was made while the nova 12.0.0 Liberty release was in development. The current version of python-novaclient at the time was 2.25.0. Once the change was merged, python-novaclient 2.26.0 was released. Since there was less than six months before 12.0.0 would be released, the deprecation cycle ran through the 13.0.0 nova server release.