test failure: unknown command diff

When I run ' ./bzr selftest -1 -s bt.test_selftest' in trunk, I get

Text attachment: traceback
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Traceback (most recent call last):
  File "/home/mbp/lib/python/testtools/runtest.py", line 143, in _run_user
    return fn(*args)
  File "/home/mbp/lib/python/testtools/testcase.py", line 539, in _run_test_method
    return self._get_test_method()()
  File "/home/mbp/bzr/work/bzrlib/tests/test_selftest.py", line 3043, in test_test_suite
    suite = tests.test_suite()
  File "/home/mbp/bzr/work/bzrlib/tests/__init__.py", line 4005, in test_suite
    plugin_suite = plugin.test_suite()
  File "/home/mbp/bzr/work/bzrlib/plugin.py", line 562, in test_suite
    return self.module.test_suite()
  File "/home/mbp/.bazaar/plugins/bzrtools/__init__.py", line 89, in test_suite
    import tests.shelf_tests
  File "/home/mbp/.bazaar/plugins/bzrtools/tests/shelf_tests.py", line 11, in <module>
    from bzrlib.plugins.bzrtools.command_classes import cmd_shelf1
  File "/home/mbp/.bazaar/plugins/bzrtools/command_classes.py", line 531, in <module>
    class cmd_cdiff(BzrToolsCommand):
  File "/home/mbp/.bazaar/plugins/bzrtools/command_classes.py", line 534, in cmd_cdiff
    takes_options = list(get_cmd_object('diff').takes_options) + [
  File "/home/mbp/bzr/work/bzrlib/commands.py", line 240, in get_cmd_object
    raise errors.BzrCommandError('unknown command "%s"' % cmd_name)
BzrCommandError: unknown command "diff"
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