class ActiveSupport::ErrorReporter

def subscribe(subscriber)

The +report+ method should never raise an error.

report(Exception, handled: Boolean, severity: (:error OR :warning OR :info), context: Hash, source: String)

Register a new error subscriber. The subscriber must respond to 
def subscribe(subscriber)
  unless subscriber.respond_to?(:report)
    raise ArgumentError, "Error subscribers must respond to #report"
  end
  @subscribers << subscriber
end