Opens the file if it's not yet open.  This call might fail with
        a :exc:`FileError`.  Not handling this error will produce an error
        that Click shows.

def open(self):
        """Opens the file if it's not yet open.  This call might fail with
        a :exc:`FileError`.  Not handling this error will produce an error
        that Click shows.
        """
        if self._f is not None:
            return self._f
        try:
            rv, self.should_close = open_stream(self.name, self.mode,
                                                self.encoding,
                                                self.errors,
                                                atomic=self.atomic)
        except (IOError, OSError) as e:
            from .exceptions import FileError
            raise FileError(self.name, hint=get_streerror(e))
        self._f = rv
        return rv