CommandContextImpl contains the following logic

public void handleSafe(String line) {
exitCode = 0;
try

{ handle(line); }

catch(Throwable t) {
final StringBuilder buf = new StringBuilder();
buf.append(t.getLocalizedMessage());
Throwable t1 = t.getCause();
while(t1 != null) {
if(t1.getLocalizedMessage() != null)

{ buf.append(": ").append(t1.getLocalizedMessage()); }

else

{ t1.printStackTrace(); }

t1 = t1.getCause();
}
error(buf.toString());
}
}

When an exception does not contain any message, e.g. in some cases IllegalArgumentException, etc, the full stacktraces are logged that are useful for debugging but not nice from the user interface point of view. It was suggested to hide them.