Exclusively create a file, only if this file previously did not exist.

def create(self):
        """Exclusively create a file, only if this file previously did not exist.
        """
        fdint = os.open(self.path, (os.O_EXCL |
                                    os.O_CREAT |
                                    os.O_RDWR))

        # XXX TODO: 'name' attribute of returned files is not mutable or
        # settable via fdopen, so this file is slighly less functional than the
        # one returned from 'open' by default.  send a patch to Python...

        return os.fdopen(fdint, 'w+b')