status can't find a shelf manager on a revision tree

Appears to have been introduced in -r5444. There's apparently no test to catch this;
" bzr --no-plugins selftest 'blackbox.*status' " passes.

bug is present up to current tip, r5504.

rory@rory-laptop:~/hack/bzr/bzr.dev$ ./bzr --no-plugins up -r-61
 M NEWS
 M bzrlib/shelf.py
 M bzrlib/status.py
 M bzrlib/tests/blackbox/test_status.py
All changes applied successfully.
Updated to revision 5444 of branch /home/rory/repos/bzr/bzr.dev
rory@rory-laptop:~/hack/bzr/bzr.dev$ ./bzr st -r1..2
modified:
  bzrlib/__init__.py
bzr: ERROR: exceptions.AttributeError: 'RevisionTree' object has no attribute 'get_shelf_manager'

Traceback (most recent call last):
  File "/home/rory/hack/bzr/bzr.dev/bzrlib/commands.py", line 912, in exception_to_return_code
    return the_callable(*args, **kwargs)
  File "/home/rory/hack/bzr/bzr.dev/bzrlib/commands.py", line 1112, in run_bzr
    ret = run(*run_argv)
  File "/home/rory/hack/bzr/bzr.dev/bzrlib/commands.py", line 690, in run_argv_aliases
    return self.run(**all_cmd_args)
  File "/home/rory/hack/bzr/bzr.dev/bzrlib/commands.py", line 705, in run
    return self._operation.run_simple(*args, **kwargs)
  File "/home/rory/hack/bzr/bzr.dev/bzrlib/cleanup.py", line 135, in run_simple
    self.cleanups, self.func, *args, **kwargs)
  File "/home/rory/hack/bzr/bzr.dev/bzrlib/cleanup.py", line 165, in _do_with_cleanups
    result = func(*args, **kwargs)
  File "/home/rory/hack/bzr/bzr.dev/bzrlib/commands.py", line 1127, in ignore_pipe
    result = func(*args, **kwargs)
  File "/home/rory/hack/bzr/bzr.dev/bzrlib/builtins.py", line 295, in run
    show_pending=(not no_pending), verbose=verbose)
  File "/home/rory/hack/bzr/bzr.dev/bzrlib/status.py", line 220, in show_tree_status
    show_ids, short, verbose))
  File "/home/rory/hack/bzr/bzr.dev/bzrlib/status.py", line 447, in _show_shelve_summary
    manager = params.new_tree.get_shelf_manager()
AttributeError: 'RevisionTree' object has no attribute 'get_shelf_manager'