It looks like something is scanning your server trying various
attacks against:

  /nuitka/xmlrpc.php

Note that nothing in roundup is php. My guess is that
the scanner/attacker is trying to post gibberish used to
exploit xmlrpc.php.

The error is odd, but without seeing what is being posted
I don't have any ideas. I assume the tracebacks stopped once
you 503'ed the url?

-- rouilj