def chattr(self, path, attr):
return SFTP_OP_UNSUPPORTED<EOL>
Change the attributes of a file.  The C{attr} object will contain
only those fields provided by the client in its request, so you
should check for the presence of fields before using them.

@param path: requested path (relative or absolute) of the file to
    change.
@type path: str
@param attr: requested attributes to change on the file.
@type attr: L{SFTPAttributes}
@return: an error code like L{SFTP_OK}.
@rtype: int