linters: yamllint config

linters: flake8 config

checker: don't hardcode linter config, load it from files

checker: go back to using hg files with -I and -X Because -X is a bit simpler than a fileset that also excludes some files (to code and just visually). Also rename property to "include" for clarity.

checker: try and catch exceptions from execute() and somewhat finish the job Exceptions coming from execute() are programming errors in checker.py, but jobs still need to tell that they are finished (and failed) to be processed by incoming.py.

checker: make run_ignore_1() a bit more flexible by adding codes argument

incoming: use a list of regular expressions to extract linter output type

incoming: move linter output matching to a function, test it

tests: pass extra arguments given to run-tests.py into pytest.main()

incoming: save filename and line number for linter output in Check.lines