Lint certbot code on Python 3, and update Pylint to the latest version (#7551)

Part of #7550

This PR makes appropriate corrections to run pylint on Python 3.

Why not keeping the dependencies unchanged and just run pylint on Python 3?
Because the old version of pylint breaks horribly on Python 3 because of unsupported version of astroid.

Why updating pylint + astroid to the latest version ?
Because this version only fixes some internal errors occuring during the lint of Certbot code, and is also ready to run gracefully on Python 3.8.

Why upgrading mypy ?
Because the old version does not support the new version of astroid required to run pylint correctly.

Why not upgrading mypy to its latest version ?
Because this latest version includes a new typshed version, that adds a lot of new type definitions, and brings dozens of new errors on the Certbot codebase. I would like to fix that in a future PR.

That said so, the work has been to find the correct set of new dependency versions, then configure pylint for sane configuration errors in our situation, disable irrelevant lintings errors, then fixing (or ignoring for good reason) the remaining mypy errors.

I also made PyLint and MyPy checks run correctly on Windows.

* Start configuration

* Reconfigure travis

* Suspend a check specific to python 3. Start fixing code.

* Repair call_args

* Fix return + elif lints

* Reconfigure development to run mainly on python3

* Remove incompatible Python 3.4 jobs

* Suspend pylint in some assertions

* Remove pylint in dev

* Take first mypy that supports typed-ast>=1.4.0 to limit the migration path

* Various return + else lint errors

* Find a set of deps that is working with current mypy version

* Update local oldest requirements

* Remove all current pylint errors

* Rebuild letsencrypt-auto

* Update mypy to fix pylint with new astroid version, and fix mypy issues

* Explain type: ignore

* Reconfigure tox, fix none path

* Simplify pinning

* Remove useless directive

* Remove debugging code

* Remove continue

* Update requirements

* Disable unsubscriptable-object check

* Disable one check, enabling two more

* Plug certbot dev version for oldest requirements

* Remove useless disable directives

* Remove useless no-member disable

* Remove no-else-* checks. Use elif in symetric branches.

* Add back assertion

* Add new line

* Remove unused pylint disable

* Remove other pylint disable

certbot-compatibility-test/certbot_compatibility_test/configurators/common.py

@@ -43,8 +43,7 @@ class Proxy(object):
         method = getattr(self._configurator, name, None)
         if callable(method):
             return method
-        else:
-            raise AttributeError()
+        raise AttributeError()
 
     def has_more_configs(self):
         """Returns true if there are more configs to test"""
@@ -82,8 +81,7 @@ class Proxy(object):
         """Returns the set of domain names that the plugin should find"""
         if self._all_names:
             return self._all_names
-        else:
-            raise errors.Error("No configuration file loaded")
+        raise errors.Error("No configuration file loaded")
 
     def get_testable_domain_names(self):
         """Returns the set of domain names that can be tested against"""

certbot-compatibility-test/certbot_compatibility_test/test_driver.py

@@ -10,7 +10,6 @@ import tempfile
 import time
 
 import OpenSSL
-from six.moves import xrange  # pylint: disable=import-error,redefined-builtin
 from urllib3.util import connection
 
 from acme import challenges
@@ -57,26 +56,27 @@ def test_authenticator(plugin, config, temp_dir):
         return False
 
     success = True
-    for i in xrange(len(responses)):
-        if not responses[i]:
+    for i, response in enumerate(responses):
+        achall = achalls[i]
+        if not response:
             logger.error(
                 "Plugin failed to complete %s for %s in %s",
-                type(achalls[i]), achalls[i].domain, config)
+                type(achall), achall.domain, config)
             success = False
-        elif isinstance(responses[i], challenges.HTTP01Response):
+        elif isinstance(response, challenges.HTTP01Response):
             # We fake the DNS resolution to ensure that any domain is resolved
             # to the local HTTP server setup for the compatibility tests
             with _fake_dns_resolution("127.0.0.1"):
-                verified = responses[i].simple_verify(
-                    achalls[i].chall, achalls[i].domain,
+                verified = response.simple_verify(
+                    achall.chall, achall.domain,
                     util.JWK.public_key(), port=plugin.http_port)
             if verified:
                 logger.info(
-                    "http-01 verification for %s succeeded", achalls[i].domain)
+                    "http-01 verification for %s succeeded", achall.domain)
             else:
                 logger.error(
                     "**** http-01 verification for %s in %s failed",
-                    achalls[i].domain, config)
+                    achall.domain, config)
                 success = False
 
     if success:
@@ -89,8 +89,7 @@ def test_authenticator(plugin, config, temp_dir):
         if _dirs_are_unequal(config, backup):
             logger.error("Challenge cleanup failed for %s", config)
             return False
-        else:
-            logger.info("Challenge cleanup succeeded")
+        logger.info("Challenge cleanup succeeded")
 
     return success
 
@@ -305,7 +304,7 @@ def get_args():
         "-e", "--enhance", action="store_true", help="tests the enhancements "
         "the plugin supports (implicitly includes installer tests)")
 
-    for plugin in PLUGINS.itervalues():
+    for plugin in PLUGINS.values():
         plugin.add_parser_arguments(parser)
 
     args = parser.parse_args()