* start typing x509.base

* statically type x509.base

* typehint X509Backend interface

* typehint at least the X509Backend interface

* make _CertificateRevocationList/_CertificateSigningRequest actual subclasses of the interface (as done before for Certificate in f16bff2cb)

* tell mypy to ignore lines with deliberately wrong types

* signature_hash_algorithm always returns a hash algorithm (it's not optional)

* Revert "signature_hash_algorithm always returns a hash algorithm (it's not optional)"

This reverts commit f6a5b172b416f8ddea561203c0cf03b55e4ec50e.

* hash algorithm is actually optional

* fix import style

* typehint parsed_version to int, which it de facto always is

* minimize changes

* break import cycle with conditional imports

* ignore access to private members of openssl implementation

* reformat code with Black

* test check for missing public key

* backend typing for twofactor package and more otp work

* even more typing

* style fixes

* no generic typing for _get_backend

* remove unneeded typing

* clean mypy with tests dir

* remove most no_type_check annotations

* le sigh

* remove unneeded comments

* switch to xdist in tox for faster runs

* not using auto to avoid too many processes on local laptops
* we need to use pytest-cov to generate coverage properly now

* these env vars aren't present on no coverage builds

* tox changes