sprockets/src/main/java/net/sf/sprockets/util/Log.java
public void w(Object src, String msg, @Nullable Throwable thrown) {
        maybeLog(WARN, src, msg, thrown);
    }
public void w(Object src, String msg, @Nullable Throwable thrown) {
        maybeLog(WARN, src, msg, thrown);
    }
Send a WARN log message and log the exception.