The documentation at
http://docs.python.org/dev/3.0/library/os.html#os.chdir doesn't specify
if the path argument to os.chdir() should be a str or a bytes, or if
maybe both are acceptable.  This is true for most of the
file-manipulating functions in the os module.

os.listdir() talks about Unicode objects.  It should probably talk about
bytes and str instead.