For just the screen capture, I don't think you need that. Sikuli has a Screen class with capture method. It can capture interactively(user selects a region) or automatically(x,y,w,h region is captured.. e.g. the entire screen)
It may also handle multi-monitors.. but I'm not sure the depth of support for them.http://doc.sikuli.or...n.html#Screen.Screen
Edit: so the basic plan would be
get captures of the warning and error dialogs.
Use Wait(image) to wait for the dialog to pop up
use Screen to take the desktop capture
I'm assuming you may run more than one script at a time so one should wait for the warning graphic, the other wait for the error graphic. Seems very intuitive since you don't have to resort to Python just for captures. Just use the built in functions.