[PATCH stable] convert: update use of deprecated bzrlib property

[Anton Shestakov]

20.07.2016, 00:16, "Kevin Bullock" <kbullock+mercurial at ringworld.org>:
> # HG changeset patch
> # User Kevin Bullock <kbullock+mercurial at ringworld.org>
> # Date 1468944032 18000
> # Tue Jul 19 11:00:32 2016 -0500
> # Branch stable
> # Node ID a5c7375e0221a5499b38638b1c6ab72f853f287b
> # Parent 754f6367122953efdc7b5539a53c99308ee90216
> convert: update use of deprecated bzrlib property

LGTM, warnings are gone.