how to detect psql's errors?

As part of renaming a database, I'm trying to script some updates to
system tables, and I can't figure out how to detect an error condition
in the SQL sent to psql.

Is there anyway to test for errors returned by psql?

For example:
echo "select foo from pg_database" | psql -U admin myDB || echo
"failed" && echo "success"

This doesn't work. Neither "failed" nor "success" are echoed.
Only 'ERROR: Attribute "foo" not found' is displayed on console.

Alternatively, is there a way to do this as a single transaction, that
will rollback if any statement fails? (Without installing PL/pgSQL,
that is.)

TIA,

Drew