Koen reported the following warnings appear when logging into an oe-core image or running grpconv:

configuration error - unknown item 'FAILLOG_ENAB' (notify administrator)
configuration error - unknown item 'LASTLOG_ENAB' (notify administrator)
configuration error - unknown item 'OBSCURE_CHECKS_ENAB' (notify administrator)
configuration error - unknown item 'PORTTIME_CHECKS_ENAB' (notify administrator)
configuration error - unknown item 'QUOTAS_ENAB' (notify administrator)
configuration error - unknown item 'MOTD_FILE' (notify administrator)
configuration error - unknown item 'FTMP_FILE' (notify administrator)
configuration error - unknown item 'NOLOGINS_FILE' (notify administrator)
configuration error - unknown item 'ENV_HZ' (notify administrator)
configuration error - unknown item 'PASS_MIN_LEN' (notify administrator)
configuration error - unknown item 'SU_WHEEL_ONLY' (notify administrator)
configuration error - unknown item 'CRACKLIB_DICTPATH' (notify administrator)
configuration error - unknown item 'PASS_CHANGE_TRIES' (notify administrator)
configuration error - unknown item 'PASS_ALWAYS_WARN' (notify administrator)
configuration error - unknown item 'CHFN_AUTH' (notify administrator)
configuration error - unknown item 'ENVIRON_FILE' (notify administrator)

These variables are coming from the default /etc/login.defs that recently started shipping with base-passwd.