tools: network and forwarder checks

Inspired by RFC8027 we implement simple checks that diagnose the sanity of network enviroment (or a forwarding resolver) for use of DNSSEC.
10 jobs from answer_checker.py in 1 minute and 43 seconds (queued for 9 seconds)
Status Job ID Name Coverage
  Test
passed #244730
docker linux amd64
test:augeas

00:00:39

passed #244736
docker linux amd64
test:comparative:kresd

00:01:30

passed #244731
docker linux amd64
test:flake8

00:00:30

passed #244737
docker linux amd64
test:latest:kresd

00:01:12

passed #244732
docker linux amd64
test:mypy

00:00:39

failed #244733
docker linux amd64
test:pylint

00:00:35

passed #244734
docker linux amd64
test:rplint

00:00:30

passed #244739
docker linux amd64
test:sanity:pdnsrecursor

00:00:33

passed #244738
docker linux amd64
test:sanity:unbound

00:00:35

passed #244735
docker linux amd64
test:unittests

00:00:31

 
Name Stage Failure
failed
test:pylint Test
Skipping Git submodules setup
$ ci/pylint-run.sh
************* Module network_check
tools/network_check.py:137:0: C0305: Trailing newlines (trailing-newlines)

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Your code has been rated at 10.00/10

ERROR: Job failed: exit code 1