public void warn(Object message, Throwable t) {
        differentiatedLog(null, CATEGORY_FQCN, LocationAwareLogger.WARN_INT, message, t);
    }
Delegates to {@link org.slf4j.Logger#warn(String,Throwable)} method in SLF4J.

@param message a message to log
@param t       a throwable to log
log4j-over-slf4j/src/main/java/org/apache/log4j/Category.java