Ah, sorry about that – it seems like the textcat.eval recipe doesn't correctly default source to None. This was already reported in this thread and will be fixed in the next release.
I just googled that strange error message and I'm not sure it's actually related to the file – maybe it occurs when Prodigy tries to start up the web server? Could you check that there's nothing else running on the host and port? (By default, localhost:8080.) And what happens when you change the port? (Either by setting "port" in your prodigy.json or via the environment variable PRODIGY_PORT.) Maybe serving on 8080 is blocked for some reason?