** unknown exception encountered, please report by visiting
**  http://mercurial.selenic.com/wiki/BugTracker
** Python 2.7.1 (r271:86832, Jun 16 2011, 16:59:05) [GCC 4.2.1 (Based on Apple Inc. build 5658) (LLVM build 2335.15.00)]
** Mercurial Distributed SCM (version 2.1+20120201)
** Extensions loaded: extdiff, rebase, progress, mq, transplant, graphlog, record, hgsubversion, fetch, patchbomb, hgattic
Traceback (most recent call last):
  File "/usr/local/bin/hg", line 38, in <module>
    mercurial.dispatch.run()
  File "/Library/Python/2.7/site-packages/mercurial/dispatch.py", line 27, in run
    sys.exit((dispatch(request(sys.argv[1:])) or 0) & 255)
  File "/Library/Python/2.7/site-packages/mercurial/dispatch.py", line 64, in dispatch
    return _runcatch(req)
  File "/Library/Python/2.7/site-packages/mercurial/dispatch.py", line 87, in _runcatch
    return _dispatch(req)
  File "/Library/Python/2.7/site-packages/mercurial/dispatch.py", line 683, in _dispatch
    cmdpats, cmdoptions)
  File "/Library/Python/2.7/site-packages/mercurial/dispatch.py", line 465, in runcommand
    ret = _runcommand(ui, options, cmd, d)
  File "/Library/Python/2.7/site-packages/mercurial/dispatch.py", line 737, in _runcommand
    return checkargs()
  File "/Library/Python/2.7/site-packages/mercurial/dispatch.py", line 691, in checkargs
    return cmdfunc()
  File "/Library/Python/2.7/site-packages/mercurial/dispatch.py", line 680, in <lambda>
    d = lambda: util.checksignature(func)(ui, *args, **cmdoptions)
  File "/Library/Python/2.7/site-packages/mercurial/util.py", line 456, in check
    return func(*args, **kwargs)
  File "/Library/Python/2.7/site-packages/mercurial/extensions.py", line 139, in wrap
    util.checksignature(origfn), *args, **kwargs)
  File "/Library/Python/2.7/site-packages/mercurial/util.py", line 456, in check
    return func(*args, **kwargs)
  File "/Users/steve/devlibs/tools/hgsubversion/hgsubversion/wrappers.py", line 487, in clone
    orig(ui, source, dest, **opts)
  File "/Library/Python/2.7/site-packages/mercurial/util.py", line 456, in check
    return func(*args, **kwargs)
  File "/Library/Python/2.7/site-packages/mercurial/commands.py", line 1157, in clone
    branch=opts.get('branch'))
  File "/Library/Python/2.7/site-packages/mercurial/extensions.py", line 184, in wrap
    return wrapper(origfn, *args, **kwargs)
  File "/Users/steve/devlibs/tools/hgsubversion/hgsubversion/wrappers.py", line 478, in hgclonewrapper
    data['srcrepo'], data['dstrepo'] = orig(ui, *args, **opts)
  File "/Library/Python/2.7/site-packages/mercurial/hg.py", line 400, in clone
    _update(destrepo, uprev)
  File "/Library/Python/2.7/site-packages/mercurial/hg.py", line 414, in update
    stats = mergemod.update(repo, node, False, False, None)
  File "/Library/Python/2.7/site-packages/mercurial/merge.py", line 580, in update
    stats = applyupdates(repo, action, wc, p2, pa, overwrite)
  File "/Library/Python/2.7/site-packages/mercurial/merge.py", line 379, in applyupdates
    subrepo.submerge(repo, wctx, mctx, wctx, overwrite)
  File "/Library/Python/2.7/site-packages/mercurial/subrepo.py", line 175, in submerge
    mctx.sub(s).get(r)
  File "/Library/Python/2.7/site-packages/mercurial/subrepo.py", line 491, in get
    self._get(state)
  File "/Library/Python/2.7/site-packages/mercurial/subrepo.py", line 481, in _get
    self._repo.root, update=False)
TypeError: 'NoneType' object is not iterable