convert: update use of deprecated bzrlib property The inventory property was deprecated in favor of root_inventory in bzr 2.5.0. Current version is 2.7.0. I noticed this when testing locally on Python 2.6.9, which has warnings turned on by default. The failure that occurs without this patch can be seen on Python 2.7 by running with warnings enabled: $ PYTHONWARNINGS=::DeprecationWarning make 'test-convert-bzr*'