def _load_configuration(conf, env_var):
    """Load default configuration settings into the given :class:`Config`
    instance and optionally try to load additional settings from the file
    pointed to by the given environmental variable.

    The environmental variable will be quietly ignored if it is not set or
    it does not point to a valid configuration file.
    """
    conf.from_object('avalon.settings')
    if env_var is None:
        return False

    # Ignore the var not being set since it's entirely reasonable
    # that a user hasn't configured it. No sense logging or printing
    # annoying things that aren't errors.
    return conf.from_envvar(env_var, silent=True)