HH-43583 add handler_404 parameter to FileMappingDispatcher
HH-43583 add an example and update docs
Merge remote-tracking branch 'origin/HH-43583' into EXP-11423
release 2.19.17 [an.sumin@hh.ru]
new debug with Jinja2
make logging more consistent
new stages, log request_time instead of app total time
improve tests
add tests for debug page
add coverage to tests run
improve frontik.testing
drop python 2.6
add new tests
self.async_group