From: Jonathan Nielsen <jonathan@...>
Date: 2010-04-16T03:30:04+09:00
Subject: Re: own exception classes

The problem (IIRC) with extending from Exception instead of
StandardError is that a plain 'rescue' statement will not catch bare
Exceptions, it catches StandardError (or is it RuntimeError?) by
default.  To catch Exception (or descended classes), you need to
specify 'rescue Exception'.  But it's a bit easier just to extend from
StandardError or RuntimeError, both of which are caught by a bare
rescue statement.

-Jonathan Nielsen