Ah, .bzr.log still has it:

0.924  opening working tree '/home/martin/ubuntu/apport/ubuntu'
1.020  preparing to commit
[11868] 2008-04-16 11:50:20.312 INFO: Committing to: /home/martin/ubuntu/apport/ubuntu/
1.102  Selecting files for commit with filter None
[11868] 2008-04-16 11:50:20.368 INFO: modified debian/changelog
[11868] 2008-04-16 11:50:20.407 INFO: modified po/de.po
1.414  added revision_id {<email address hidden>}
1.449  Auto-packing repository <bzrlib.repofmt.pack_repo.RepositoryPackCollection object at 0xe90610>, which h
as 15 pack files, containing 1370 revisions into 11 packs.
1.580  Traceback (most recent call last):
  File "/usr/lib/python2.5/site-packages/bzrlib/commands.py", line 834, in run_bzr_catch_errors
    return run_bzr(argv)
  File "/usr/lib/python2.5/site-packages/bzrlib/commands.py", line 790, in run_bzr
    ret = run(*run_argv)
  File "/usr/lib/python2.5/site-packages/bzrlib/commands.py", line 492, in run_argv_aliases
    return self.run(**all_cmd_args)
  File "/usr/lib/python2.5/site-packages/bzrlib/builtins.py", line 2355, in run
    author=author)
  File "/usr/lib/python2.5/site-packages/bzrlib/decorators.py", line 165, in write_locked
    return unbound(self, *args, **kwargs)
  File "/usr/lib/python2.5/site-packages/bzrlib/workingtree_4.py", line 246, in commit
    result = WorkingTree3.commit(self, message, revprops, *args, **kwargs)
  File "/usr/lib/python2.5/site-packages/bzrlib/decorators.py", line 165, in write_locked
    return unbound(self, *args, **kwargs)
  File "/usr/lib/python2.5/site-packages/bzrlib/mutabletree.py", line 187, in commit
    revprops=revprops, *args, **kwargs)
  File "/usr/lib/python2.5/site-packages/bzrlib/commit.py", line 373, in commit
    self.rev_id = self.builder.commit(self.message)
  File "/usr/lib/python2.5/site-packages/bzrlib/repository.py", line 139, in commit
    self.repository.commit_write_group()
  File "/usr/lib/python2.5/site-packages/bzrlib/repository.py", line 919, in commit_write_group
    self._commit_write_group()
  File "/usr/lib/python2.5/site-packages/bzrlib/repofmt/pack_repo.py", line 2013, in _commit_write_group
    return self._pack_collection._commit_write_group()
  File "/usr/lib/python2.5/site-packages/bzrlib/repofmt/pack_repo.py", line 1666, in _commit_write_group
    if not self.autopack():
  File "/usr/lib/python2.5/site-packages/bzrlib/repofmt/pack_repo.py", line 1231, in autopack
    self._execute_pack_operations(pack_operations)
  File "/usr/lib/python2.5/site-packages/bzrlib/repofmt/pack_repo.py", line 1250, in _execute_pack_operations
    self._save_pack_names(clear_obsolete_packs=True)
  File "/usr/lib/python2.5/site-packages/bzrlib/repofmt/pack_repo.py", line 1587, in _save_pack_names
    self.transport.list_dir('obsolete_packs'))
  File "/usr/lib/python2.5/site-packages/bzrlib/transport/local.py", line 453, in list_dir
    self._translate_error(e, path)
  File "/usr/lib/python2.5/site-packages/bzrlib/transport/__init__.py", line 347, in _translate_error
    raise errors.NoSuchFile(path, extra=e)
NoSuchFile: No such file: u'/home/martin/ubuntu/apport/ubuntu/.bzr/repository/obsolete_packs': [Errno 2] No such file or directory: '/home/martin/ubuntu/apport/ubuntu/.bzr/repository/obsolete_packs'