I just stumbled across this problem when starting "idle3" in a directory containing a copy of textwrap.py which was not compatible with python3.

In issue13506 idle3 was changed to behave like the regular python shell, i.e. as described here in this issue, and since my ~/.pythonrc.py imports readline, I could reproduce this problem by creating a bogus readline.py file and starting a python interpreter.

So besides being a security issue when starting python or idle in untrusted directories, it may cause technical issues when working in directories containing .py files with certain names.