'Load the settings module pointed to by the environment variable. This
is used the first time we need any settings at all, if the user has not
previously configured the settings manually.'

def _setup(self):

    try:
        settings_module = os.environ[ENVIRONMENT_VARIABLE]
        if (not settings_module):
            raise KeyError
    except KeyError:
        raise ImportError(('Settings    cannot    be    imported,    because    environment    variable    %s    is    undefined.' % ENVIRONMENT_VARIABLE))
    self._wrapped = Settings(settings_module)
