Enable mypy strict mode (#8766)

Built on top of #8748, this PR reenables mypy strict mode and adds the appropriate corrections to pass the types checks.

* Upgrade mypy

* First step for acme

* Cast for the rescue

* Fixing types for certbot

* Fix typing for certbot-nginx

* Finalize type fixes, configure no optional strict check for mypy in tox

* Align requirements

* Isort

* Pylint

* Protocol for python 3.6

* Use Python 3.9 for mypy, make code compatible with Python 3.8<

* Pylint and mypy

* Pragma no cover

* Pythonic NotImplemented constant

* More type definitions

* Add comments

* Simplify typing logic

* Use vararg tuple

* Relax constraints on mypy

* Add more type

* Do not silence error if target is not defined

* Conditionally import Protocol for type checking only

* Clean up imports

* Add comments

* Align python version linting with mypy and coverage

* Just ignore types in an unused module

* Add comments

* Fix lint

* Work in progress

* Finish type control

* Isort

* Fix pylint

* Fix imports

* Fix cli subparser

* Some fixes

* Coverage

* Remove --no-strict-optional (obviously...)

* Update certbot-apache/certbot_apache/_internal/configurator.py

Co-authored-by: Brad Warren <bmw@users.noreply.github.com>

* Update certbot/certbot/_internal/display/completer.py

Co-authored-by: Brad Warren <bmw@users.noreply.github.com>

* Cleanup dns_google

* Improve lock controls and fix subparser

* Use the expected interfaces

* Fix code

Co-authored-by: Brad Warren <bmw@users.noreply.github.com>

certbot-dns-gehirn/certbot_dns_gehirn/_internal/dns_gehirn.py

@@ -1,12 +1,15 @@
 """DNS Authenticator for Gehirn Infrastructure Service DNS."""
 import logging
+from typing import Optional
 
 from lexicon.providers import gehirn
 import zope.interface
 
+from certbot import errors
 from certbot import interfaces
 from certbot.plugins import dns_common
 from certbot.plugins import dns_common_lexicon
+from certbot.plugins.dns_common import CredentialsConfiguration
 
 logger = logging.getLogger(__name__)
 
@@ -27,7 +30,7 @@ class Authenticator(dns_common.DNSAuthenticator):
 
     def __init__(self, *args, **kwargs):
         super(Authenticator, self).__init__(*args, **kwargs)
-        self.credentials = None
+        self.credentials: Optional[CredentialsConfiguration] = None
 
     @classmethod
     def add_parser_arguments(cls, add):  # pylint: disable=arguments-differ
@@ -57,6 +60,8 @@ class Authenticator(dns_common.DNSAuthenticator):
         self._get_gehirn_client().del_txt_record(domain, validation_name, validation)
 
     def _get_gehirn_client(self):
+        if not self.credentials:  # pragma: no cover
+            raise errors.Error("Plugin has not been prepared.")
         return _GehirnLexiconClient(
             self.credentials.conf('api-token'),
             self.credentials.conf('api-secret'),