Thanks for the feedback!

It's on line 111 in test_collections.py::

        n = 10000
        import string, random
        names = [''.join([random.choice(string.letters) for j in
range(10)]) for i in range(n)]
        Big = namedtuple('Big', names)
        b = Big(*range(n))

I think the condition is triggered because Big's __new__ (which seems to
be dynamically generated by namedtuple using exec) has an argument list
with 10000 arguments.

Ok, I'm now looking through SVN logs and have already added some more
changes to my patchset.

Thanks, I had changed MAGIC but didn't know that marshal.c uses it.

So I won't handle documentation in this issue then.