Make ON_ERROR_STOP stop on shell script failure

Hi,

"""\set ON_ERROR_STOP on""" stops any subsequent incoming query that 
comes after an error of an SQL, but does not stop after a shell script 
ran by """\! <some command>""" returning values other than 0, -1, or 
127, which suggests a failure in the result of the shell script.

For example, suppose that below is an SQL file.
\set ON_ERROR_STOP on
SELECT 1;
\! false
SELECT 2;

The current design allows SELECT 2 even though the shell script returns 
a value indicating a failure.

I thought that this action is rather unexpected since, based on the word 
"""ON_ERROR_STOP""", ones may expect that failures of shell scripts 
should halt the incoming instructions as well.
One clear solution is to let failures of shell script stop incoming 
queries just like how errors of SQLs do currently. Thoughts?

Tatsu