Tor integration tests started failing

[exarkun]

Traceback (most recent call last):
  File "/usr/lib/python2.7/runpy.py", line 174, in _run_module_as_main
    "__main__", fname, loader, pkg_name)
  File "/usr/lib/python2.7/runpy.py", line 72, in _run_code
    exec code in run_globals
  File "/tmp/tahoetFY24U/chutney/lib/chutney/TorNet.py", line 1499, in <module>
    sys.exit(main())
  File "/tmp/tahoetFY24U/chutney/lib/chutney/TorNet.py", line 1493, in main
    result = runConfigFile(args['action'], f.read())
  File "/tmp/tahoetFY24U/chutney/lib/chutney/TorNet.py", line 1474, in runConfigFile
    return getattr(network, verb)()
  File "/tmp/tahoetFY24U/chutney/lib/chutney/TorNet.py", line 1295, in configure
    self._checkConfig()
  File "/tmp/tahoetFY24U/chutney/lib/chutney/TorNet.py", line 1267, in _checkConfig
    n.getBuilder().checkConfig(self)
  File "/tmp/tahoetFY24U/chutney/lib/chutney/TorNet.py", line 563, in checkConfig
    self._createTorrcFile(checkOnly=True)
  File "/tmp/tahoetFY24U/chutney/lib/chutney/TorNet.py", line 507, in _createTorrcFile
    fn_out = self._getTorrcFname()
  File "/tmp/tahoetFY24U/chutney/lib/chutney/TorNet.py", line 410, in _getTorrcFname
    return self.expand("${torrc_fname}")
  File "/tmp/tahoetFY24U/chutney/lib/chutney/TorNet.py", line 406, in expand
    return chutney.Templating.Template(pat, includePath).format(self._env)
  File "/tmp/tahoetFY24U/chutney/lib/chutney/Templating.py", line 384, in format
    values = PathDict(values)
  File "/tmp/tahoetFY24U/chutney/lib/chutney/Templating.py", line 289, in __init__
    path = os.getenv('PATH').split(":")
AttributeError: 'NoneType' object has no attribute 'split'

[exarkun]

Some changes were made to Chutney that introduced this behavior. See ​https://gitweb.torproject.org/chutney.git/commit/?id=0a83ecfaa1d406a5cfd502da6d7e367b64eaad86

[exarkun]

​https://github.com/tahoe-lafs/tahoe-lafs/pull/637

[exarkun]

​https://github.com/tahoe-lafs/tahoe-lafs/commit/56b46ee900bda43db14b99e291561c52332505a8