fix new mypy and pylint errors
See Job #354630 and job #354620.
tools/answer_checker.py:35: error: On Python 3 '%s' % b'abc' produces "b'abc'"; use %r if this is a desired behavior
and
pydnstest/scenario.py:683:16: R1724: Unnecessary "else" after "continue" (no-else-continue)
pydnstest/scenario.py:732:12: R1724: Unnecessary "else" after "continue" (no-else-continue)