Ensure notifications are sent even in the case of an error

Exceptions are intended to create their own notifications, at least if they occur in the request cycle.

i.e. hitting an action:

def my_action

 transaction do
   raise "Some Error"
 end

end

should generate a few events:

%w(sql.active_record sql.active_record error.action_controller perform_action.active_controller) # possibly more that I'm forgetting

that'll let plugins like exception notification basically instrument via this kind of thing:

ActiveSupport::Notifications.subscribe('error.action_controller') do |event|
  ExceptionNotifier.notify( ... ) 
end

This is all only my unclear understanding - comments?

Gotcha. +1

We need to tell someway to the subscriber that the event failed. Maybe adding an exception key with the exception class name and message.