dnspython 2.0 and linter fixes

See merge request !186

Accessing module attributes with _underscore names was a bad idea from
the very beginning so this commit removes assert depending on this. IMHO
it is not worth the trouble.

Container upgrade + logging tweaks

See merge request !185

- matchpart tracebacks were simple duplicate
- usually we do not need full traceback anyway so let's print it only
  in VERBOSE=1 mode

py.test version 6.0.0 refuses -k parameter values with / characters,
so we have to adapt.

unbound: disable trust anchor signaling

See merge request !105

TA signaling in newer versions of Unbound breaks old tests
which do not contain answers for RFC 8145 queries.

This does not work with older versions of Unbound but hopefully these
are too old now for anyone to care.

fix leaking sockets

See merge request !183

The old code worked most of the time thanks to garbage collector,
but obviously it was unreliable/a coincidence.

world_mx_nic_www.rpl: generalize a NODATA answer

See merge request !182

We started hitting undefined answer for www.nic.mx DS.

dnspython 2.0.0 compatibility

See merge request !181

Compatibility with https://github.com/rthalley/dnspython/issues/482

deckard.py: start the server without `start_new_session`

Closes #3

See merge request !172

This hopefully prevents the daemons from hanging after ^C exit.

networking: assign proper network masks for addresses

See merge request !180

resolver: remove implementation-specific iter_refuse test

See merge request !179

The original test was hard to interpred and very much depends on
behavior of specific resolver implementation. For this reason I removed
it from the generic Deckard repo and I'm going to replace it by
kresd-specific test in kresd repo.

networking: use proper wrapper around ip command

Closes #48

See merge request !178

Remove bundled libfaketime

See merge request !176

add pyroute2 to requirements for future use

See merge request !177

ci: make pylint work again with the new Docker image

See merge request !175

deckard.py: fix scenarios with no stub-addr config option

See merge request !174

DNAME tests

See merge request !171

resolver: new test val_bogus_nodata

See merge request !173