After upgrading from Struts 2.3.x to 2.5.x we noticed a stack trace in our logs which was not previously present. The error is actually quite minor and doesn't impact any functionality, the problem is we have no ability to control its presence in our logs do the way the Dispatcher.java prints directly to the console.
This can be seen in class org.apache.struts2.dispatcher.Dispatcher around line 586
Only after the error is printed is a check made on whether to handle it. The exception is then rethrown.
I think it would make more sense to use the logging framework to log exceptions or otherwise give us some control over whether this appears. As it is it's impossible to turn it off.