def rmdir(self, path):
return SFTP_OP_UNSUPPORTED<EOL>
Remove a directory if it exists.  The C{path} should refer to an
existing, empty folder -- otherwise this method should return an
error.

@param path: requested path (relative or absolute) of the folder
    to remove.
@type path: str
@return: an SFTP error code like L{SFTP_OK}.
@rtype: int