This is somewhat obscure to notice but the problem is towards that
getattr on attr_matches. For "int" specifically, it will try to get the
attribute '__abstractmethods__' (which is a member of int.__class__) and
will raise an AttributeError but then the exception is discarded by the
readline module.
A workaround is to change that getattr to:

try:
    val = getattr(object, word)
except AttributeError:
    continue