Rather than pointing the 'project usage list' entry point directly to
ListUsage, this makes a ListProjectUsage subclass to alias the desired
command and still allow for changing behaviour or issuing a deprecation
messages. This implementation simply sets a new 'deprecated' attribute
in the command class that cliff will use to skip this command when
generating help output.
The actual skipping of the command in help output is dependant on
https://review.openstack.org/147349 merging in cliff, this review will
simply have no effect on help output until a version of cliff with
that update is present.
The deprecation message printed is somewhat generic until
https://review.openstack.org/147381 is merged in cliff.
Until that is merged, the deprecation message will not have the name
of the actual command given by the user in it, but rather the text
'this command'.
Closes-bug: #1406654
Change-Id: Ie08d4f88d71a660fca1862405351109cd0aa86b6
bc11c4d7d8