Common message for single slave selections.

tool/CommandSiiRead.cpp

@@ -62,9 +62,7 @@ void CommandSiiRead::execute(MasterDevice &m, const StringVector &args)
     slaves = selectedSlaves(m);
 
     if (slaves.size() != 1) {
-        err << "'" << getName() << "' requires a single slave ("
-            << slaves.size() << " selected).";
-        throwInvalidUsageException(err);
+        throwSingleSlaveRequired(slaves.size());
     }
     slave = &slaves.front();
     data.slave_position = slave->position;