def logStarted(build, step, log):
    """A new Log has been started, probably because a step has just
        started running a shell command. 'log' is the IStatusLog object
        which can be queried for more information.

        This method may return an IStatusReceiver (such as 'self'), in which
        case the target's logChunk method will be invoked as text is added to
        the logfile. This receiver will automatically be unsubsribed when the
        log finishes."""
