* Make type checking more strict.
* mypy: warn about unreachable code.
* Enable warn_redundant_casts.
* Enable strict_bytes.
* Look at some warn_return_any warnings.
* Move mypy/flake8/isort config files to more 'natural' places.
* Add pylint.
* Look at no-member.
* Look at pointless-* and unnecessary-pass.
* Look at useless-*.
* Lint.