Code review comment for lp://staging/~vila/ubuntu-ci-services-itself/secgroups

Could we refactor this so that we use it in tests/run.py to clean up
*just* the security groups that were created in the test run (minus
precious)?

+ # FIXME: There is probably a better way, but for now, just require
+ # that unit_config defines 'juju_env' and be done. -- vila
+ # 2014-02-17
+ auth_conf.get('juju_env')

tests/run.py handles this well:

    juju_env = os.environ.get('JUJU_ENV')
    if juju_env is None:
        juju_env = envs.get('default')
    if not juju_env:
        log.error('No juju environment specified.')
        sys.exit(1)