before: revspec trying to write to branch with read-only lock

bzr log -r before:
 in dir /home/buildslave/slaves/twisted/bot-idnar-debian64/easy-no-zope-2.6debian/Twisted (timeout 1200 secs)
 watching logfiles {}
 argv: ['bzr', 'log', '-r', 'before:']
 environment:
  HOME=/home/buildslave
  LANG=en_US.UTF-8
  LOGNAME=buildslave
  MAKEFLAGS=w
  MAKELEVEL=1
  MFLAGS=-w
  PATH=/home/buildslave/.local/bin:/usr/local/bin:/usr/bin:/bin
  PWD=/home/buildslave/slaves/twisted/bot-idnar-debian64/easy-no-zope-2.6debian/Twisted
  SHELL=/bin/sh
 using PTY: False
bzr: ERROR: bzrlib.errors.ReadOnlyError: A write attempt was made in a read only transaction on LockableFiles(lock, file:///home/buildslave/slaves/twisted/bot-idnar-debian64/easy-no-zope-2.6debian/Twisted/.bzr/branch/)

Traceback (most recent call last):
  File "/usr/lib/python2.6/dist-packages/bzrlib/commands.py", line 853, in exception_to_return_code
    return the_callable(*args, **kwargs)
  File "/usr/lib/python2.6/dist-packages/bzrlib/commands.py", line 1055, in run_bzr
    ret = run(*run_argv)
  File "/usr/lib/python2.6/dist-packages/bzrlib/commands.py", line 661, in run_argv_aliases
    return self.run_direct(**all_cmd_args)
  File "/usr/lib/python2.6/dist-packages/bzrlib/commands.py", line 665, in run_direct
    return self._operation.run_simple(*args, **kwargs)
  File "/usr/lib/python2.6/dist-packages/bzrlib/cleanup.py", line 122, in run_simple
    self.cleanups, self.func, *args, **kwargs)
  File "/usr/lib/python2.6/dist-packages/bzrlib/cleanup.py", line 156, in _do_with_cleanups
    result = func(*args, **kwargs)
  File "/usr/lib/python2.6/dist-packages/bzrlib/commands.py", line 1070, in ignore_pipe
    result = func(*args, **kwargs)
  File "/usr/lib/python2.6/dist-packages/bzrlib/builtins.py", line 2337, in run
    rev1, rev2 = _get_revision_range(revision, b, self.name())
  File "/usr/lib/python2.6/dist-packages/bzrlib/builtins.py", line 2401, in _get_revision_range
    rev1 = rev2 = revisionspec_list[0].in_history(branch)
  File "/usr/lib/python2.6/dist-packages/bzrlib/revisionspec.py", line 222, in in_history
    return self._match_on_and_check(branch, revs)
  File "/usr/lib/python2.6/dist-packages/bzrlib/revisionspec.py", line 201, in _match_on_and_check
    info = self._match_on(branch, revs)
  File "/usr/lib/python2.6/dist-packages/bzrlib/revisionspec.py", line 550, in _match_on
    r = RevisionSpec.from_string(self.spec)._match_on(branch, revs)
  File "/usr/lib/python2.6/dist-packages/bzrlib/revisionspec.py", line 327, in _match_on
    return self._try_spectype(rs_class, branch)
  File "/usr/lib/python2.6/dist-packages/bzrlib/revisionspec.py", line 309, in _try_spectype
    return rs.in_history(branch)
  File "/usr/lib/python2.6/dist-packages/bzrlib/revisionspec.py", line 222, in in_history
    return self._match_on_and_check(branch, revs)
  File "/usr/lib/python2.6/dist-packages/bzrlib/revisionspec.py", line 201, in _match_on_and_check
    info = self._match_on(branch, revs)
  File "/usr/lib/python2.6/dist-packages/bzrlib/revisionspec.py", line 817, in _match_on
    branch.fetch(other_branch, revision_b)
  File "/usr/lib/python2.6/dist-packages/bzrlib/decorators.py", line 192, in write_locked
    self.lock_write()
  File "/usr/lib/python2.6/dist-packages/bzrlib/branch.py", line 2144, in lock_write
    return self.control_files.lock_write(token=token)
  File "/usr/lib/python2.6/dist-packages/bzrlib/lockable_files.py", line 188, in lock_write
    raise errors.ReadOnlyError(self)
ReadOnlyError: A write attempt was made in a read only transaction on LockableFiles(lock, file:///home/buildslave/slaves/twisted/bot-idnar-debian64/easy-no-zope-2.6debian/Twisted/.bzr/branch/)

bzr 2.1.2 on python 2.6.6 (Linux-2.6.32-5-amd64-x86_64-with-debian-6.0.6)
arguments: ['/usr/bin/bzr', 'log', '-r', 'before:']
encoding: 'UTF-8', fsenc: 'UTF-8', lang: 'en_US.UTF-8'
plugins:
  bzrtools /usr/lib/python2.6/dist-packages/bzrlib/plugins/bzrtools [2.1.0]
  launchpad /usr/lib/python2.6/dist-packages/bzrlib/plugins/launchpad [2.1.2]
  netrc_credential_store /usr/lib/python2.6/dist-packages/bzrlib/plugins/netrc_credential_store [2.1.2]
  news_merge /usr/lib/python2.6/dist-packages/bzrlib/plugins/news_merge [2.1.2]
  svn /home/buildslave/.bazaar/plugins/svn [1.0.2]

*** 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.