Get cursor name for invalid_cursor_name error

How to reliable get cursor name which cause invalid_cursor_name error?

postgres=# CREATE FUNCTION value_from_cursor_unsafe(cursor_name text)
RETURNS integer
postgres-# STRICT LANGUAGE plpgsql
postgres-# AS $$
postgres$# DECLARE
postgres$# cursor CONSTANT refcursor NOT NULL := cursor_name;
postgres$# result integer;
postgres$# BEGIN
postgres$# FETCH FIRST FROM cursor INTO result;
postgres$# return result;
postgres$# END
postgres$# $$;
CREATE FUNCTION
postgres=# CREATE FUNCTION value_from_cursor_safe(cursor_name text)
RETURNS integer
postgres-# STRICT LANGUAGE plpgsql
postgres-# AS $$
postgres$# DECLARE
postgres$# result integer;
postgres$# BEGIN
postgres$# BEGIN
postgres$# result := value_from_cursor_unsafe(cursor_name);
postgres$# EXCEPTION
postgres$# WHEN invalid_cursor_name THEN
postgres$# RAISE INFO '%', SQLERRM;
postgres$# END;
postgres$# return result;
postgres$# END
postgres$# $$;
CREATE FUNCTION
postgres=# SELECT value_from_cursor_safe('asd'); -- case 1
INFO: cursor "asd" does not exist
value_from_cursor_safe
------------------------

(1 row)

postgres=# BEGIN;
BEGIN
postgres=*# DECLARE "fgh" SCROLL CURSOR FOR VALUES
(value_from_cursor_unsafe('jkl'));
DECLARE CURSOR
postgres=*# SELECT value_from_cursor_safe('fgh'); -- case 2
INFO: cursor "jkl" does not exist
value_from_cursor_safe
------------------------

(1 row)

postgres=*# COMMIT;
COMMIT

For example, in given example in "case 2" I want to rethrow error,
because it is not about 'fgh' cursor, which I directly query. But it
seems cursor name only available as part of localizable error message,
but not as separate field through GET STACKED DIAGNOSTICS.