bzr crashes when running fast-import plugin. `AttributeError: 'CHKInventoryRepository' object has no attribute 'get_ancestry'`

****@localhost ~/Code/C/CPP (fossil)-[trunk] % fossil export --git ./CPP.fossil | bzr fast-import -
23:59:01 Starting import ...
23:59:01 Found 79 commits already loaded - skipping over these ...
23:59:01 Updating branch information ...
bzr: ERROR: exceptions.AttributeError: 'CHKInventoryRepository' object has no attribute 'get_ancestry'

Traceback (most recent call last):
  File "/usr/lib/python2.7/site-packages/bzrlib/commands.py", line 930, in exception_to_return_code
    return the_callable(*args, **kwargs)
  File "/usr/lib/python2.7/site-packages/bzrlib/commands.py", line 1121, in run_bzr
    ret = run(*run_argv)
  File "/usr/lib/python2.7/site-packages/bzrlib/commands.py", line 673, in run_argv_aliases
    return self.run(**all_cmd_args)
  File "/usr/lib/python2.7/site-packages/bzrlib/commands.py", line 697, in run
    return self._operation.run_simple(*args, **kwargs)
  File "/usr/lib/python2.7/site-packages/bzrlib/cleanup.py", line 136, in run_simple
    self.cleanups, self.func, *args, **kwargs)
  File "/usr/lib/python2.7/site-packages/bzrlib/cleanup.py", line 166, in _do_with_cleanups
    result = func(*args, **kwargs)
  File "/usr/lib/python2.7/site-packages/bzrlib/plugins/fastimport/cmds.py", line 312, in run
    user_map=user_map)
  File "/usr/lib/python2.7/site-packages/bzrlib/plugins/fastimport/cmds.py", line 42, in _run
    return proc.process(p.iter_commands)
  File "/usr/lib/python2.7/site-packages/bzrlib/plugins/fastimport/processors/generic_processor.py", line 310, in process
    super(GenericProcessor, self)._process(command_iter)
  File "/usr/lib/python2.7/site-packages/fastimport/processor.py", line 79, in _process
    self.post_process()
  File "/usr/lib/python2.7/site-packages/bzrlib/plugins/fastimport/processors/generic_processor.py", line 351, in post_process
    branches_updated, branches_lost = updater.update()
  File "/usr/lib/python2.7/site-packages/bzrlib/plugins/fastimport/branch_updater.py", line 61, in update
    if self._update_branch(br, tip):
  File "/usr/lib/python2.7/site-packages/bzrlib/plugins/fastimport/branch_updater.py", line 168, in _update_branch
    ancestry = self.repo.get_ancestry(last_rev_id)
AttributeError: 'CHKInventoryRepository' object has no attribute 'get_ancestry'

bzr 2.6.0 on python 2.7.5 (Linux-3.11.6-1-ARCH-x86_64-with-glibc2.2.5)
arguments: ['/usr/bin/bzr', 'fast-import', '-']
plugins: bash_completion[2.6.0], changelog_merge[2.6.0], explorer[1.3.0],
    fastimport[0.14.0dev], git[0.6.12], grep[2.6.0], gtk[0.100.0],
    launchpad[2.6.0], netrc_credential_store[2.6.0], news_merge[2.6.0],
    po_merge[2.6.0], qbzr[0.23.0], weave_fmt[2.6.0]
encoding: 'ascii', fsenc: 'utf8', lang: 'C'

*** Bazaar has encountered an internal error. This probably indicates a
    bug in Bazaar. You can help us fix it by filing a bug report at
        https://bugs.launchpad.net/bzr/+filebug
    including this traceback and a description of the problem.