bzr-builddeb strips two "-X" blocks from the end of the version instead of only one, when looking for the upstream tarball

Example: The pulseaudio packaging branch, which is merge-mode:
lp:~ubuntu-audio-dev/pulseaudio/ubuntu.natty

It uses nasty version numbers containing lots of hyphens:
$ dpkg-parsechangelog
Source: pulseaudio
Version: 1:0.9.22+stable-queue-18-geb966-0ubuntu2

$ bzr bd-do
Looking for a way to retrieve the upstream tarball
...
bzr: ERROR: Unable to find the needed upstream tarball: pulseaudio_0.9.22+stable-queue-18.orig.tar.gz.

Expected: pulseaudio_0.9.22+stable-queue-18-geb966.orig.tar.gz.

Cause:
builddeb/cmds.py:
upstream_provider = UpstreamProvider(changelog.package,·
                changelog.version.upstream_version,

When _tarball_names() in the upstream provider uses self.version.upstream_version