No warnings or errors after same sequential revoke

[Alex Ignatov <a.ignatov@xxxxxxxxxxxxxx>]

Hello!
Why we have no warnings  or errors about that  we have no such grant after first revoke?
postgres=> grant select(i2) on table user1.t2 to user2;
GRANT
postgres=> revoke select(i2) on table user1.t2 from user2;

REVOKE

postgres=> revoke select(i2) on table user1.t2 from user2;

REVOKE

postgres=> revoke select(i2) on table user1.t2 from user2;

REVOKE

postgres=> revoke select(i2) on table user1.t2 from user2;

REVOKE

No warnings about that this grant is not available.
It looks like revoking nonexisting grants is allowed???

-- 
Alex Ignatov
Postgres Professional: http://www.postgrespro.com
The Russian Postgres Company