Is there a GUI for informing a user of missing dependencies?

[Jason]

I'm writing a small GUI (Python 2.5/6) using wxPython and pySerial.
Since these are both 3rd party modules, if a user doesn't have them
installed and tries to run the GUI from a file browser, the app will
fail silently. I'm hoping to avoid that.

Sure, I'll have a readme file, but I was wondering if there is an even
more direct way. I was going to roll my own (eg. very simple Tkinter
fallback error dialog if wxPython import fails, wxPython error dialog
if anything else is missing); but I was wondering if such a system
already exists out there.

— Jason