How to use argparse.ArgumentError in Python
<p>I'd like to use the ArgumentError exception in the argparse module in Python, but I can't figure out how to use it.  The signature says that it should be called as <code>ArgumentError(argument, message)</code>, but I can't figure out what <code>argument</code> should be.  I think it should be some part of the parser object, but I couldn't find any documentation for it.</p>
