RD-11280: a schema does not exist error isn't reported to the user

[bgaidioz]

It should be reported to the user. Note the query is a little peculiar: in place of an alias column name, the person entered a single quoted string (a regular string). With a regular identifier the error doesn't occur.

We already do catch errors due to typos in schema names since a long time, and receive them as "undefined table" (status 42). When people type SELECT FROM country.list. That new error code is seen when someone types this kind of code:

SELECT
 airport_id,
 city,
 country.name 'cname' -- <== the alias 'cname' is entered with quotes, as a string

Only then it complains of "country" not existing as a schema name, using 3F.