If `iface` is available, return interface info and no error, otherwise
    return no info and log and return an error

def _get_iface_info(iface):
    '''
    If `iface` is available, return interface info and no error, otherwise
    return no info and log and return an error
    '''
    iface_info = interfaces()

    if iface in iface_info.keys():
        return iface_info, False
    else:
        error_msg = ('Interface "{0}" not in available interfaces: "{1}"'
                     ''.format(iface, '", "'.join(iface_info.keys())))
        log.error(error_msg)
        return None, error_msg