traceback from hg serve

[James Gregory]

Hg is serving repositories from the built-in mercurial server. Nginx
is acting as a proxy for handling authorization etc.

A continuous integration server is polling frepositories (via the
nginx proxy) for changes, but it keeps resulting in tracebacks, which
look like this:

127.0.0.1 - - [23/Apr/2014 16:56:20] Exception happened during
processing request '/hg/traintracs/workbench/?cmd=capabilities':
Traceback (most recent call last):
  File "/usr/local/lib/python2.7/dist-packages/mercurial/hgweb/server.py",
line 80, in do_POST
    self.do_write()
  File "/usr/local/lib/python2.7/dist-packages/mercurial/hgweb/server.py",
line 73, in do_write
    self.do_hgweb()
  File "/usr/local/lib/python2.7/dist-packages/mercurial/hgweb/server.py",
line 140, in do_hgweb
    for chunk in self.server.application(env, self._start_response):
  File "/usr/local/lib/python2.7/dist-packages/mercurial/hgweb/hgwebdir_mod.py",
line 153, in __call__
    return self.run_wsgi(req)
  File "/usr/local/lib/python2.7/dist-packages/mercurial/hgweb/hgwebdir_mod.py",
line 217, in run_wsgi
    repo = hg.repository(self.ui, real)
  File "/usr/local/lib/python2.7/dist-packages/mercurial/hg.py", line
113, in repository
    peer = _peerorrepo(ui, path, create)
  File "/usr/local/lib/python2.7/dist-packages/mercurial/hg.py", line
103, in _peerorrepo
  File "/usr/local/lib/python2.7/dist-packages/mercurial/localrepo.py",
line 2449, in instance
    obj = _peerlookup(path).instance(ui, path, create)
    return localrepository(ui, util.urllocalpath(path), create)
  File "/usr/local/lib/python2.7/dist-packages/mercurial/localrepo.py",
line 174, in __init__
    self.ui = baseui.copy()
  File "/usr/local/lib/python2.7/dist-packages/mercurial/ui.py", line
49, in copy
    return self.__class__(self)
  File "/usr/local/lib/python2.7/dist-packages/mercurial/ui.py", line
29, in __init__
    self._tcfg = src._tcfg.copy()
  File "/usr/local/lib/python2.7/dist-packages/mercurial/config.py",
line 53, in copy
    return config(self)
  File "/usr/local/lib/python2.7/dist-packages/mercurial/config.py",
line 49, in __init__
    for k in data._data:
RuntimeError: dictionary changed size during iteration

Anyone know why this might be?

-- 
James