def valid_env_vars() -> bool:
    """Validate that required env vars exist.

    :returns: True if required env vars exist.

    .. versionadded:: 0.0.12
    """
    for envvar in _REQUIRED_ENV_VARS:
        try:
            _check_env_var(envvar)
        except KeyError as ex:
            LOG.error(ex)
            sys.exit(1)
    return True