Code review comment for lp:~thumper/python-jujuclient/jes-cache-file

I have not been able to run the tests for some reason, and I am unfamiliar with tox:

$ JUJU_TEST_ENV="mary2" tox -e py27
Traceback (most recent call last):
  File "/usr/bin/tox", line 9, in <module>
    load_entry_point('tox==1.6.0', 'console_scripts', 'tox')()
  File "/usr/lib/python2.7/dist-packages/tox/_cmdline.py", line 25, in main
    config = parseconfig(args, 'tox')
  File "/usr/lib/python2.7/dist-packages/tox/_config.py", line 44, in parseconfig
    parseini(config, inipath)
  File "/usr/lib/python2.7/dist-packages/tox/_config.py", line 236, in __init__
    config)
  File "/usr/lib/python2.7/dist-packages/tox/_config.py", line 292, in _makeenvconfig
    vc.setenv = reader.getdict(section, 'setenv')
  File "/usr/lib/python2.7/dist-packages/tox/_config.py", line 419, in getdict
    s = self.getdefault(section, name, None)
  File "/usr/lib/python2.7/dist-packages/tox/_config.py", line 511, in getdefault
    x = self._replace(x)
  File "/usr/lib/python2.7/dist-packages/tox/_config.py", line 618, in _replace
    return rexpattern.sub(replace_func, x)
  File "/usr/lib/python2.7/dist-packages/tox/_config.py", line 609, in _replace_match_no_quote
    return self._replace_match(match, quote=False)
  File "/usr/lib/python2.7/dist-packages/tox/_config.py", line 604, in _replace_match
    return handler(match, quote)
  File "/usr/lib/python2.7/dist-packages/tox/_config.py", line 541, in _replace_env
    (envkey, envkey))
tox.ConfigError: ConfigError: substitution env:'JUJU_TEST_ENV:"test"': unkown environment variable 'JUJU_TEST_ENV:"test"'