Add isort and flake8 to CI (#869)

* Run isort.

* Clean up unused assignments.

* Add flake8 linting step.

plugins/module_utils/crypto/module_backends/certificate_entrust.py

@@ -6,37 +6,39 @@
 # SPDX-License-Identifier: GPL-3.0-or-later
 
 from __future__ import absolute_import, division, print_function
+
+
 __metaclass__ = type
 
 
 import datetime
 import os
 
-from ansible.module_utils.common.text.converters import to_native, to_bytes
-
-from ansible_collections.community.crypto.plugins.module_utils.ecs.api import ECSClient, RestOperationException, SessionConfigurationException
-
-from ansible_collections.community.crypto.plugins.module_utils.crypto.support import (
-    load_certificate,
-)
-
+from ansible.module_utils.common.text.converters import to_bytes, to_native
 from ansible_collections.community.crypto.plugins.module_utils.crypto.cryptography_support import (
     CRYPTOGRAPHY_TIMEZONE,
     cryptography_serial_number_of_cert,
     get_not_valid_after,
 )
-
 from ansible_collections.community.crypto.plugins.module_utils.crypto.module_backends.certificate import (
-    CertificateError,
     CertificateBackend,
+    CertificateError,
     CertificateProvider,
 )
-
+from ansible_collections.community.crypto.plugins.module_utils.crypto.support import (
+    load_certificate,
+)
+from ansible_collections.community.crypto.plugins.module_utils.ecs.api import (
+    ECSClient,
+    RestOperationException,
+    SessionConfigurationException,
+)
 from ansible_collections.community.crypto.plugins.module_utils.time import (
     get_now_datetime,
     get_relative_time_option,
 )
 
+
 try:
     from cryptography.x509.oid import NameOID
 except ImportError:
@@ -157,7 +159,7 @@ class EntrustCertificateBackend(CertificateBackend):
         cert_details = {}
         try:
             self._ensure_existing_certificate_loaded()
-        except Exception as dummy:
+        except Exception:
             return
         if self.existing_certificate:
             serial_number = None