I know this topic is quite old but...
I am also interested in the topic you were, but I still got no answers. Meanwhile, I have partially solved (or avoided) your problem as you described it:
QuoteI need to make sure that certain character styles are defined in the current Scribus document.
by ensuring a given Master Page is loaded, something you can check via something similar to:
def checkValidMasterPage(self,masterPageName):
# if CD Sleeve is not a defined as a masterpage in the current document, we cannot use it
if masterPageName not in scribus.masterPageNames():
scribus.messageBox('Usage Error', 'You need a CD Sleeve Document open', icon=0, button1=1)
sys.exit(2)
Good luck if you are still around!
It would be nice if the new API makes life easier in dealing with styles.