I don't really like the "--avoid-pgauthid" option, but "--no-passwords" would probably work.
'--no-passwords' is a good alternative.
Would submit a patch soon.
After reviewing further, it seems that merely adding a password related workaround wouldn't suffice. Further --no-password is already an alias for -w, so that flag is effectively taken.
Since the main restriction with AWS RDS is the unavailability of pg_authid, probably that is a better basis to name the flag on.
Attaching a patch to add a new flag (--no-pgauthid) to pg_dumpall that can dump Globals without needing pg_authid. So the following works with AWS RDS Postgres databases.
pg_dumpall --no-pgauthid --globals-only > a.sql
I'll create a Commitfest entry, if there aren't many objections.
