Before tackling this, I'd like a precision on os.rename(src, dst)
semantics. The documentation says "If dst is a directory, OSError will
be raised". However, under Linux, if src is a directory and dst is an
empty directory, dst is overwritten with src:

$ mkdir src dst
$ touch dst/t
$ ./python -c "import os; os.rename('src', 'dst')"
Traceback (most recent call last):
  File "<string>", line 1, in <module>
OSError: [Errno 39] Directory not empty
$ rm dst/t
$ ./python -c "import os; os.rename('src', 'dst')"
$ 

Is this a bug, a misfeature, or just an imprecision in the documentation?