Jython has no os.access (nor os.chmod)

Simple patch

Does os.access not work on Jython, or is it just missing entirely? If it's missing, I'd much rather catch an AttributeError ("better to ask forgiveness than permission"). Please verify one way or the other and I'll check this in.

Jacob: it's missing entirely. But I don't quite like to wrap the entire catching AttributeError?, as it could hide real errors.

Straight-forward patch. Possible alternative:

def _make_writeable(filename):
    "Makes sure that the file is writeable. Useful if our source is read-only."
    import stat
    if sys.platform.startswith('java'):
        return # On Jython there is no os.access() 
    if not os.access(filename, os.W_OK):
	st = os.stat(filename)
	new_permissions = stat.S_IMODE(st.st_mode) | stat.S_IWUSR
	os.chmod(filename, new_permissions)

(In [6281]) Fixed #5443 -- Handle lack of os.access() and os.chmod() in Jython. Thanks, Leo Soto.