我无法在我的机器上更新 mercurial repos。进行更新时出现以下错误hg up --traceback：
Traceback (most recent call last):
File "/usr/lib/python2.7/dist-packages/mercurial/dispatch.py", line 87, in _runcatch
return _dispatch(req)
File "/usr/lib/python2.7/dist-packages/mercurial/dispatch.py", line 679, in _dispatch
cmdpats, cmdoptions)
File "/usr/lib/python2.7/dist-packages/mercurial/dispatch.py", line 454, in runcommand
ret = _runcommand(ui, options, cmd, d)
File "/usr/lib/python2.7/dist-packages/mercurial/dispatch.py", line 733, in _runcommand
return checkargs()
File "/usr/lib/python2.7/dist-packages/mercurial/dispatch.py", line 687, in checkargs
return cmdfunc()
File "/usr/lib/python2.7/dist-packages/mercurial/dispatch.py", line 676, in <lambda>
d = lambda: util.checksignature(func)(ui, *args, **cmdoptions)
File "/usr/lib/python2.7/dist-packages/mercurial/util.py", line 385, in check
return func(*args, **kwargs)
File "/usr/lib/python2.7/dist-packages/mercurial/commands.py", line 5131, in update
ret = hg.update(repo, rev)
File "/usr/lib/python2.7/dist-packages/mercurial/hg.py", line 395, in update
stats = mergemod.update(repo, node, False, False, None)
File "/usr/lib/python2.7/dist-packages/mercurial/merge.py", line 554, in update
stats = applyupdates(repo, action, wc, p2, pa, overwrite)
File "/usr/lib/python2.7/dist-packages/mercurial/merge.py", line 329, in applyupdates
subrepo.submerge(repo, wctx, mctx, wctx.ancestor(mctx), overwrite)
File "/usr/lib/python2.7/dist-packages/mercurial/subrepo.py", line 156, in submerge
mctx.sub(s).get(r)
File "/usr/lib/python2.7/dist-packages/mercurial/subrepo.py", line 668, in get
if self._svnversion >= (1, 5):
File "/usr/lib/python2.7/dist-packages/mercurial/util.py", line 169, in __get__
result = self.func(obj)
File "/usr/lib/python2.7/dist-packages/mercurial/subrepo.py", line 567, in _svnversion
output, err = self._svncommand(['--version'], filename=None)
File "/usr/lib/python2.7/dist-packages/mercurial/subrepo.py", line 555, in _svncommand
universal_newlines=True, env=env, **extrakw)
File "/usr/lib/python2.7/subprocess.py", line 679, in __init__
errread, errwrite)
File "/usr/lib/python2.7/subprocess.py", line 1239, in _execute_child
raise child_exception
OSError: [Errno 2] No such file or directory
abort: No such file or directory
我尝试做rm -rf myrepo然后做，hg clone ssh://hg@bitbucket.org/myrepo但是该命令正确下载了 repo，但是当 hg 尝试将 repo 更新为分支默认值时，我得到了同样的错误，更具体地说，我得到了这个：
destination directory: foo
requesting all changes
adding changesets
adding manifests
adding file changes
added 6270 changesets with 20990 changes to 3682 files
updating to branch default
abort: No such file or directory
使用引用，我得到一个类似于我之前得到的错误。我什至尝试在我的系统上重新安装 mercurial，但没有任何运气。
你能指出是什么问题吗。回购头似乎没问题，（我可以clone在update其他机器上），我可以在我的系统上clone或update其他 hg 回购。这与子回购有什么关系吗？引用暗示了这一点。
我的系统详细信息：32 位 Ubuntu 11.10，运行 mercurial 版本 1.9.1。