adding scaliest
SI-8019 Make Publisher check PartialFunction is defined for Event

Reactions are PartialFunctions, so if events come through
indiscriminately that the listener is not defined for, errors occur. Eg:

--
Exception in thread "AWT-EventQueue-0" scala.MatchError: FocusGained(scala.swing wrapper scala.swing.TextField
--

A Coursera thread with people affected by this issue:

https://class.coursera.org/reactive-001/forum/thread?thread_id=1315
SI-8495 swing.Publisher does not always notify all listeners

The ‘listeners’ need to be copied to prevent changes while it’s being
used.

This is the second bug in listeners code and another fix that will slow
it down. Looks like a prime candidate for a rewrite.