diff --git a/puppet/zulip_ops/files/zulip-ec2-configure-interfaces b/puppet/zulip_ops/files/zulip-ec2-configure-interfaces
index 4f630828d9..9f813dcdc5 100755
--- a/puppet/zulip_ops/files/zulip-ec2-configure-interfaces
+++ b/puppet/zulip_ops/files/zulip-ec2-configure-interfaces
@@ -1,5 +1,4 @@
 #!/usr/bin/env python3
-# -*- coding: utf-8 -*-
 #
 # Copyright © 2013 Zulip, Inc.
 #
@@ -42,7 +41,6 @@ interfaces.
 
 '''
 
-from __future__ import absolute_import
 import sys
 import logging
 import logging.handlers
diff --git a/zerver/migrations/0273_migrate_old_bot_messages.py b/zerver/migrations/0273_migrate_old_bot_messages.py
index 2d4be1ad0b..ef44361190 100644
--- a/zerver/migrations/0273_migrate_old_bot_messages.py
+++ b/zerver/migrations/0273_migrate_old_bot_messages.py
@@ -1,6 +1,3 @@
-# -*- coding: utf-8 -*-
-from __future__ import unicode_literals
-
 from django.conf import settings
 from django.db import migrations
 from django.db.backends.postgresql.schema import DatabaseSchemaEditor
diff --git a/zerver/migrations/0276_alertword.py b/zerver/migrations/0276_alertword.py
index 17498d0784..75d3eafb3c 100644
--- a/zerver/migrations/0276_alertword.py
+++ b/zerver/migrations/0276_alertword.py
@@ -1,5 +1,3 @@
-# -*- coding: utf-8 -*-
-
 from django.conf import settings
 from django.db import migrations, models
 import django.db.models.deletion
diff --git a/zerver/migrations/0277_migrate_alert_word.py b/zerver/migrations/0277_migrate_alert_word.py
index 2ed1d3422f..158e823aa5 100644
--- a/zerver/migrations/0277_migrate_alert_word.py
+++ b/zerver/migrations/0277_migrate_alert_word.py
@@ -1,5 +1,3 @@
-# -*- coding: utf-8 -*-
-
 from django.db import migrations
 from django.db.backends.postgresql_psycopg2.schema import DatabaseSchemaEditor
 from django.db.migrations.state import StateApps
diff --git a/zerver/tests/test_alert_words.py b/zerver/tests/test_alert_words.py
index 929a3cc4d4..3b19e4abae 100644
--- a/zerver/tests/test_alert_words.py
+++ b/zerver/tests/test_alert_words.py
@@ -66,14 +66,14 @@ class AlertWordTests(ZulipTestCase):
         self.assert_length(realm_alert_words[user.id], 3)
 
         # Test the case-insensitivity of adding words
-        do_add_alert_words(user, set(["ALert", "ALERT"]))
+        do_add_alert_words(user, {"ALert", "ALERT"})
         words = user_alert_words(user)
         self.assertEqual(set(words), set(self.interesting_alert_word_list))
         realm_alert_words = alert_words_in_realm(user.realm)
         self.assert_length(realm_alert_words[user.id], 3)
 
         # Test the case-insensitivity of removing words
-        do_remove_alert_words(user, set(["ALert"]))
+        do_remove_alert_words(user, {"ALert"})
         words = user_alert_words(user)
         self.assertEqual(set(words), set(self.interesting_alert_word_list) - {'alert'})
         realm_alert_words = alert_words_in_realm(user.realm)
diff --git a/zerver/tests/test_auth_backends.py b/zerver/tests/test_auth_backends.py
index 0c1ae24197..e2b771a5a5 100644
--- a/zerver/tests/test_auth_backends.py
+++ b/zerver/tests/test_auth_backends.py
@@ -2840,8 +2840,8 @@ class ExternalMethodDictsTests(ZulipTestCase):
             external_auth_methods = get_external_method_dicts(get_realm("zephyr"))
             # Both idps enabled for the zephyr realm, + github auth.
             self.assert_length(external_auth_methods, 3)
-            self.assertEqual(set([external_auth_methods[0]['name'], external_auth_methods[1]['name']]),
-                             set(['saml:test_idp', 'saml:test_idp2']))
+            self.assertEqual({external_auth_methods[0]['name'], external_auth_methods[1]['name']},
+                             {'saml:test_idp', 'saml:test_idp2'})
 
 class FetchAuthBackends(ZulipTestCase):
     def assert_on_error(self, error: Optional[str]) -> None: