Evil code from the Python standard library

Question

So, we have had this: http://lucumr.pocoo.org/2009/3/1/the-1000-speedup-or-the-stdlib-sucks. It demonstrates a rather bad bug that is probably costing the universe a load of cycles even as we speak. It's fixed now, which is great.

So what parts of the standard library have you noticed to be evil?

I would expect all the responsible people to match up an answer with a bug report (if suitable) and a patch (if superman).

Answer 1

Never attribute to malice that which can be adequately explained by stupidity.

Answer 2

The rexec module has so many security holes in it that it's almost useless.

Answer 3

(since this is a different module, placing it in a different answer)

cgitb has some weird threading issues. See this bug report.