> Mmmh, the problem with Perl's approach is that it changes the current
> working directory (calls to chdir()), which is process-specific and not
> thread-specific. Currently, no function in shutil changes the current
> working directory, which is a nice behaviour and should IMO be preserved.

Using chdir() makes sense and it doesn't look like a too big problem to me:

def rmtree(...):
    ...
    curdir = os.getcwd()
    try:
        call chdir() as required
    finally:
        try:
            os.chdir(curdir)
        except:
            warnings.warn("Unable to chdir to previous current dir")
    ...