bogus error message for ALTER TABLE ALTER CONSTRAINT

I just discovered that trying to set a foreign key as NO INHERIT in
ALTER TABLE ALTER CONSTRAINT returns an absurd error message:

create table pk (a int primary key);
create table fk (a int references pk);

alter table fk alter constraint fk_a_fkey deferrable, alter constraint fk_a_fkey no inherit;
ERROR: ALTER CONSTRAINT statement constraints cannot be marked NO INHERIT

The explanation is that somebody misunderstood what must be given to
processCASbits in 2013. The intended message is:
ERROR: FOREIGN KEY constraints cannot be marked NO INHERIT

Here's the fix along with some additional cleanup.

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Álvaro Herrera Breisgau, Deutschland — https://www.EnterpriseDB.com/