Add isort and flake8 to CI (#869)

* Run isort.

* Clean up unused assignments.

* Add flake8 linting step.

plugins/modules/openssh_keypair.py

@@ -6,6 +6,8 @@
 # SPDX-License-Identifier: GPL-3.0-or-later
 
 from __future__ import absolute_import, division, print_function
+
+
 __metaclass__ = type
 
 DOCUMENTATION = r"""
@@ -202,9 +204,8 @@ comment:
 """
 
 from ansible.module_utils.basic import AnsibleModule
-
 from ansible_collections.community.crypto.plugins.module_utils.openssh.backends.keypair_backend import (
-    select_backend
+    select_backend,
 )