Check python interactive mode in sitecustomize
<p>I have a MOTD-type message which prints on invocation of the interpreter. Currently this is printed up in sitecustomize. I'd like to suppress the message if the interpreter is not in interactive mode; unfortunately all of the checks in 
<a href="http://stackoverflow.com/questions/2356399/tell-if-python-is-in-interactive-mode">Tell if python is in interactive mode</a> do not work in sitecustomize. (<code>sys.argv</code>, <code>sys.ps1</code>, <code>__main__.__file__</code> are not populated.) Are there checks which work in sitecustomize?</p>
