Basic set of tests with focus on this flow:
1. add set of subscriptions

  2. add set of handlers

  3. trigger sequence of "interesting" events

  4. collect indications

  5. and make assertions as needed
Currently the assertions are mostly that correct classes have been

delivered, reporting the events in correct order.
~~
This is followup to request #1741.
Since then:

Rewrote old and added missing docstrings
TestIndicationEventStream now inherits from

IndicationStreamTestCase instead using it as mixin
fixed typos
removed unnecessary CLASS_NAME and NEEDS_INDICATIONS
made handlers option explicit instead of using

default_driver_args
fixed xtest* typos