diff --git a/synapse/config/__init__.py b/synapse/config/__init__.py
index 1e76e9559df6..d2f889159e75 100644
--- a/synapse/config/__init__.py
+++ b/synapse/config/__init__.py
@@ -1,4 +1,3 @@
-# -*- coding: utf-8 -*-
 # Copyright 2014-2016 OpenMarket Ltd
 #
 # Licensed under the Apache License, Version 2.0 (the "License");
diff --git a/synapse/config/__main__.py b/synapse/config/__main__.py
index 65043d5b5b5f..3a7f995f5bca 100644
--- a/synapse/config/__main__.py
+++ b/synapse/config/__main__.py
@@ -1,4 +1,3 @@
-# -*- coding: utf-8 -*-
 # Copyright 2015, 2016 OpenMarket Ltd
 #
 # Licensed under the Apache License, Version 2.0 (the "License");
@@ -32,5 +31,5 @@
         print(getattr(config, key))
         sys.exit(0)
     else:
-        sys.stderr.write("Unknown command %r\n" % (action,))
+        sys.stderr.write(f"Unknown command {action!r}\n")
         sys.exit(1)
diff --git a/synapse/config/_base.py b/synapse/config/_base.py
index ba9cd63cf2d5..b1341fe499a5 100644
--- a/synapse/config/_base.py
+++ b/synapse/config/_base.py
@@ -1,4 +1,3 @@
-# -*- coding: utf-8 -*-
 # Copyright 2014-2016 OpenMarket Ltd
 # Copyright 2017-2018 New Vector Ltd
 # Copyright 2019 The Matrix.org Foundation C.I.C.
@@ -188,7 +187,7 @@ def path_exists(cls, file_path):
     @classmethod
     def check_file(cls, file_path, config_name):
         if file_path is None:
-            raise ConfigError("Missing config for %s." % (config_name,))
+            raise ConfigError(f"Missing config for {config_name}.")
         try:
             os.stat(file_path)
         except OSError as e:
@@ -207,7 +206,7 @@ def ensure_directory(cls, dir_path):
             if e.errno != errno.EEXIST:
                 raise
         if not os.path.isdir(dir_path):
-            raise ConfigError("%s is not a directory" % (dir_path,))
+            raise ConfigError(f"{dir_path} is not a directory")
         return dir_path
 
     @classmethod
@@ -313,12 +312,12 @@ def __init__(self):
 
         for config_class in self.config_classes:
             if config_class.section is None:
-                raise ValueError("%r requires a section name" % (config_class,))
+                raise ValueError(f"{config_class!r} requires a section name")
 
             try:
                 conf = config_class(self)
             except Exception as e:
-                raise Exception("Failed making %s: %r" % (config_class.section, e))
+                raise Exception(f"Failed making {config_class.section}: {e!r}")
             self._configs[config_class.section] = conf
 
     def __getattr__(self, item: str) -> Any:
@@ -354,7 +353,7 @@ def _get_unclassed_config(self, asking_section: Optional[str], item: str):
             if item in dir(val):
                 return getattr(val, item)
 
-        raise AttributeError(item, "not found in %s" % (list(self._configs.keys()),))
+        raise AttributeError(item, "not found in {}".format(list(self._configs.keys())))
 
     def invoke_all(self, func_name: str, *args, **kwargs) -> MutableMapping[str, Any]:
         """
@@ -668,7 +667,7 @@ def load_or_generate_config(cls, description, argv):
 
             (config_path,) = config_files
             if not path_exists(config_path):
-                print("Generating config file %s" % (config_path,))
+                print(f"Generating config file {config_path}")
 
                 if config_args.data_directory:
                     data_dir_path = config_args.data_directory
@@ -915,7 +914,7 @@ def read_file(file_path: Any, config_path: Iterable[str]) -> str:
         with open(file_path) as file_stream:
             return file_stream.read()
     except OSError as e:
-        raise ConfigError("Error accessing file %r" % (file_path,), config_path) from e
+        raise ConfigError(f"Error accessing file {file_path!r}", config_path) from e
 
 
 __all__ = [
diff --git a/synapse/config/_util.py b/synapse/config/_util.py
index 8fce7f6bb133..3edb4b71068f 100644
--- a/synapse/config/_util.py
+++ b/synapse/config/_util.py
@@ -1,4 +1,3 @@
-# -*- coding: utf-8 -*-
 # Copyright 2020 The Matrix.org Foundation C.I.C.
 #
 # Licensed under the Apache License, Version 2.0 (the "License");
diff --git a/synapse/config/api.py b/synapse/config/api.py
index 55c038c0c4ee..1521073039ca 100644
--- a/synapse/config/api.py
+++ b/synapse/config/api.py
@@ -32,7 +32,7 @@ def read_config(self, config: JsonDict, **kwargs):
 
     def generate_config_section(cls, **kwargs) -> str:
         formatted_default_state_types = "\n".join(
-            "           # - %s" % (t,) for t in _DEFAULT_PREJOIN_STATE_TYPES
+            f"           # - {t}" for t in _DEFAULT_PREJOIN_STATE_TYPES
         )
 
         return """\
@@ -45,7 +45,7 @@ def generate_config_section(cls, **kwargs) -> str:
            # By default, the following state event types are shared with users who
            # receive invites to the room:
            #
-%(formatted_default_state_types)s
+{formatted_default_state_types}
            #
            # Uncomment the following to disable these defaults (so that only the event
            # types listed in 'additional_event_types' are shared). Defaults to 'false'.
@@ -59,9 +59,9 @@ def generate_config_section(cls, **kwargs) -> str:
            #
            #additional_event_types:
            #  - org.example.custom.event.type
-        """ % {
-            "formatted_default_state_types": formatted_default_state_types
-        }
+        """.format(
+            formatted_default_state_types=formatted_default_state_types
+        )
 
     def _get_prejoin_state_types(self, config: JsonDict) -> Iterable[str]:
         """Get the event types to include in the prejoin state
diff --git a/synapse/config/appservice.py b/synapse/config/appservice.py
index 746fc3cc02f6..7391d8579c8a 100644
--- a/synapse/config/appservice.py
+++ b/synapse/config/appservice.py
@@ -64,7 +64,7 @@ def load_appservices(hostname, config_files):
 
     for config_file in config_files:
         try:
-            with open(config_file, "r") as f:
+            with open(config_file) as f:
                 appservice = _load_appservice(hostname, yaml.safe_load(f), config_file)
                 if appservice.id in seen_ids:
                     raise ConfigError(
@@ -97,15 +97,13 @@ def _load_appservice(hostname, as_info, config_filename):
     required_string_fields = ["id", "as_token", "hs_token", "sender_localpart"]
     for field in required_string_fields:
         if not isinstance(as_info.get(field), str):
-            raise KeyError(
-                "Required string field: '%s' (%s)" % (field, config_filename)
-            )
+            raise KeyError(f"Required string field: '{field}' ({config_filename})")
 
     # 'url' must either be a string or explicitly null, not missing
     # to avoid accidentally turning off push for ASes.
     if not isinstance(as_info.get("url"), str) and as_info.get("url", "") is not None:
         raise KeyError(
-            "Required string field or explicit null: 'url' (%s)" % (config_filename,)
+            f"Required string field or explicit null: 'url' ({config_filename})"
         )
 
     localpart = as_info["sender_localpart"]
diff --git a/synapse/config/auth.py b/synapse/config/auth.py
index 9aabaadf9e54..e10d641a9655 100644
--- a/synapse/config/auth.py
+++ b/synapse/config/auth.py
@@ -1,4 +1,3 @@
-# -*- coding: utf-8 -*-
 # Copyright 2015, 2016 OpenMarket Ltd
 # Copyright 2020 The Matrix.org Foundation C.I.C.
 #
diff --git a/synapse/config/cache.py b/synapse/config/cache.py
index 4e8abbf88aeb..29d89c77ef00 100644
--- a/synapse/config/cache.py
+++ b/synapse/config/cache.py
@@ -1,4 +1,3 @@
-# -*- coding: utf-8 -*-
 # Copyright 2019 Matrix.org Foundation C.I.C.
 #
 # Licensed under the Apache License, Version 2.0 (the "License");
@@ -185,9 +184,7 @@ def read_config(self, config, **kwargs):
 
         for cache, factor in individual_factors.items():
             if not isinstance(factor, (int, float)):
-                raise ConfigError(
-                    "caches.per_cache_factors.%s must be a number" % (cache,)
-                )
+                raise ConfigError(f"caches.per_cache_factors.{cache} must be a number")
             self.cache_factors[cache] = factor
 
         # Resize all caches (if necessary) with the new factors we've loaded
diff --git a/synapse/config/cas.py b/synapse/config/cas.py
index dbf50859659f..901f4123e187 100644
--- a/synapse/config/cas.py
+++ b/synapse/config/cas.py
@@ -1,4 +1,3 @@
-# -*- coding: utf-8 -*-
 # Copyright 2015, 2016 OpenMarket Ltd
 #
 # Licensed under the Apache License, Version 2.0 (the "License");
diff --git a/synapse/config/consent_config.py b/synapse/config/consent_config.py
index c47f364b146d..30d07cc219bc 100644
--- a/synapse/config/consent_config.py
+++ b/synapse/config/consent_config.py
@@ -1,4 +1,3 @@
-# -*- coding: utf-8 -*-
 # Copyright 2018 New Vector Ltd
 #
 # Licensed under the Apache License, Version 2.0 (the "License");
diff --git a/synapse/config/database.py b/synapse/config/database.py
index e7889b9c20a3..8b26bab59a33 100644
--- a/synapse/config/database.py
+++ b/synapse/config/database.py
@@ -1,4 +1,3 @@
-# -*- coding: utf-8 -*-
 # Copyright 2014-2016 OpenMarket Ltd
 # Copyright 2020 The Matrix.org Foundation C.I.C.
 #
@@ -87,7 +86,7 @@ def __init__(self, name: str, db_config: dict):
         db_engine = db_config.get("name", "sqlite3")
 
         if db_engine not in ("sqlite3", "psycopg2"):
-            raise ConfigError("Unsupported database type %r" % (db_engine,))
+            raise ConfigError(f"Unsupported database type {db_engine!r}")
 
         if db_engine == "sqlite3":
             db_config.setdefault("args", {}).update(
diff --git a/synapse/config/emailconfig.py b/synapse/config/emailconfig.py
index 52505ac5d2b5..c587939c7a7a 100644
--- a/synapse/config/emailconfig.py
+++ b/synapse/config/emailconfig.py
@@ -1,4 +1,3 @@
-# -*- coding: utf-8 -*-
 # Copyright 2015-2016 OpenMarket Ltd
 # Copyright 2017-2018 New Vector Ltd
 # Copyright 2019 The Matrix.org Foundation C.I.C.
diff --git a/synapse/config/experimental.py b/synapse/config/experimental.py
index eb96ecda74ea..a693fba87779 100644
--- a/synapse/config/experimental.py
+++ b/synapse/config/experimental.py
@@ -1,4 +1,3 @@
-# -*- coding: utf-8 -*-
 # Copyright 2021 The Matrix.org Foundation C.I.C.
 #
 # Licensed under the Apache License, Version 2.0 (the "License");
diff --git a/synapse/config/federation.py b/synapse/config/federation.py
index 55e4db54425d..090ba047fa23 100644
--- a/synapse/config/federation.py
+++ b/synapse/config/federation.py
@@ -1,4 +1,3 @@
-# -*- coding: utf-8 -*-
 # Copyright 2020 The Matrix.org Foundation C.I.C.
 #
 # Licensed under the Apache License, Version 2.0 (the "License");
diff --git a/synapse/config/groups.py b/synapse/config/groups.py
index 7b7860ea713f..15c2e64bda2f 100644
--- a/synapse/config/groups.py
+++ b/synapse/config/groups.py
@@ -1,4 +1,3 @@
-# -*- coding: utf-8 -*-
 # Copyright 2017 New Vector Ltd
 #
 # Licensed under the Apache License, Version 2.0 (the "License");
diff --git a/synapse/config/homeserver.py b/synapse/config/homeserver.py
index 64a2429f7787..130953506825 100644
--- a/synapse/config/homeserver.py
+++ b/synapse/config/homeserver.py
@@ -1,4 +1,3 @@
-# -*- coding: utf-8 -*-
 # Copyright 2014-2016 OpenMarket Ltd
 # Copyright 2018 New Vector Ltd
 #
diff --git a/synapse/config/jwt_config.py b/synapse/config/jwt_config.py
index f30330abb6d5..9e07e7300814 100644
--- a/synapse/config/jwt_config.py
+++ b/synapse/config/jwt_config.py
@@ -1,4 +1,3 @@
-# -*- coding: utf-8 -*-
 # Copyright 2015 Niklas Riekenbrauck
 #
 # Licensed under the Apache License, Version 2.0 (the "License");
diff --git a/synapse/config/key.py b/synapse/config/key.py
index 350ff1d6654c..77f787d2c047 100644
--- a/synapse/config/key.py
+++ b/synapse/config/key.py
@@ -1,4 +1,3 @@
-# -*- coding: utf-8 -*-
 # Copyright 2015, 2016 OpenMarket Ltd
 # Copyright 2019 The Matrix.org Foundation C.I.C.
 #
@@ -170,7 +169,7 @@ def generate_config_section(
         base_key_name = os.path.join(config_dir_path, server_name)
 
         if generate_secrets:
-            macaroon_secret_key = 'macaroon_secret_key: "%s"' % (
+            macaroon_secret_key = 'macaroon_secret_key: "{}"'.format(
                 random_string_with_symbols(50),
             )
             form_secret = 'form_secret: "%s"' % random_string_with_symbols(50)
@@ -292,7 +291,7 @@ def read_signing_keys(self, signing_key_path, name):
         try:
             return read_signing_keys(signing_keys.splitlines(True))
         except Exception as e:
-            raise ConfigError("Error reading %s: %s" % (name, str(e)))
+            raise ConfigError("Error reading {}: {}".format(name, str(e)))
 
     def read_old_signing_keys(self, old_signing_keys):
         if old_signing_keys is None:
@@ -307,7 +306,7 @@ def read_old_signing_keys(self, old_signing_keys):
                 keys[key_id] = verify_key
             else:
                 raise ConfigError(
-                    "Unsupported signing algorithm for old key: %r" % (key_id,)
+                    f"Unsupported signing algorithm for old key: {key_id!r}"
                 )
         return keys
 
@@ -322,7 +321,7 @@ def generate_files(self, config, config_dir_path):
             )
 
         if not self.path_exists(signing_key_path):
-            print("Generating signing key file %s" % (signing_key_path,))
+            print(f"Generating signing key file {signing_key_path}")
             with open(signing_key_path, "w") as signing_key_file:
                 key_id = "a_" + random_string(4)
                 write_signing_keys(signing_key_file, (generate_signing_key(key_id),))
diff --git a/synapse/config/logger.py b/synapse/config/logger.py
index 999aecce5c78..b174e0df6d54 100644
--- a/synapse/config/logger.py
+++ b/synapse/config/logger.py
@@ -1,4 +1,3 @@
-# -*- coding: utf-8 -*-
 # Copyright 2014-2016 OpenMarket Ltd
 #
 # Licensed under the Apache License, Version 2.0 (the "License");
diff --git a/synapse/config/metrics.py b/synapse/config/metrics.py
index 2b289f4208d0..7ac82edb0ed1 100644
--- a/synapse/config/metrics.py
+++ b/synapse/config/metrics.py
@@ -1,4 +1,3 @@
-# -*- coding: utf-8 -*-
 # Copyright 2015, 2016 OpenMarket Ltd
 # Copyright 2019 The Matrix.org Foundation C.I.C.
 #
diff --git a/synapse/config/oidc_config.py b/synapse/config/oidc_config.py
index 05733ec41dcb..5fb94376fdb0 100644
--- a/synapse/config/oidc_config.py
+++ b/synapse/config/oidc_config.py
@@ -1,4 +1,3 @@
-# -*- coding: utf-8 -*-
 # Copyright 2020 Quentin Gliech
 # Copyright 2020-2021 The Matrix.org Foundation C.I.C.
 #
diff --git a/synapse/config/password_auth_providers.py b/synapse/config/password_auth_providers.py
index 85d07c4f8f2a..1cf69734bb5f 100644
--- a/synapse/config/password_auth_providers.py
+++ b/synapse/config/password_auth_providers.py
@@ -1,4 +1,3 @@
-# -*- coding: utf-8 -*-
 # Copyright 2016 Openmarket
 #
 # Licensed under the Apache License, Version 2.0 (the "License");
diff --git a/synapse/config/push.py b/synapse/config/push.py
index 7831a2ef7921..6ef8491caf4b 100644
--- a/synapse/config/push.py
+++ b/synapse/config/push.py
@@ -1,4 +1,3 @@
-# -*- coding: utf-8 -*-
 # Copyright 2015, 2016 OpenMarket Ltd
 # Copyright 2017 New Vector Ltd
 #
diff --git a/synapse/config/redis.py b/synapse/config/redis.py
index 1373302335b3..33104af73472 100644
--- a/synapse/config/redis.py
+++ b/synapse/config/redis.py
@@ -1,4 +1,3 @@
-# -*- coding: utf-8 -*-
 # Copyright 2020 The Matrix.org Foundation C.I.C.
 #
 # Licensed under the Apache License, Version 2.0 (the "License");
diff --git a/synapse/config/registration.py b/synapse/config/registration.py
index f27d1e14acba..02da41dd5162 100644
--- a/synapse/config/registration.py
+++ b/synapse/config/registration.py
@@ -1,4 +1,3 @@
-# -*- coding: utf-8 -*-
 # Copyright 2015, 2016 OpenMarket Ltd
 #
 # Licensed under the Apache License, Version 2.0 (the "License");
@@ -126,7 +125,7 @@ def read_config(self, config, **kwargs):
         self.auto_join_rooms = config.get("auto_join_rooms", [])
         for room_alias in self.auto_join_rooms:
             if not RoomAlias.is_valid(room_alias):
-                raise ConfigError("Invalid auto_join_rooms entry %s" % (room_alias,))
+                raise ConfigError(f"Invalid auto_join_rooms entry {room_alias}")
 
         # Options for creating auto-join rooms if they do not exist yet.
         self.autocreate_auto_join_rooms = config.get("autocreate_auto_join_rooms", True)
@@ -191,7 +190,7 @@ def read_config(self, config, **kwargs):
 
     def generate_config_section(self, generate_secrets=False, **kwargs):
         if generate_secrets:
-            registration_shared_secret = 'registration_shared_secret: "%s"' % (
+            registration_shared_secret = 'registration_shared_secret: "{}"'.format(
                 random_string_with_symbols(50),
             )
         else:
diff --git a/synapse/config/repository.py b/synapse/config/repository.py
index 061c4ec83fc7..146bc55d6f77 100644
--- a/synapse/config/repository.py
+++ b/synapse/config/repository.py
@@ -1,4 +1,3 @@
-# -*- coding: utf-8 -*-
 # Copyright 2014, 2015 OpenMarket Ltd
 #
 # Licensed under the Apache License, Version 2.0 (the "License");
diff --git a/synapse/config/room.py b/synapse/config/room.py
index 692d7a19361e..d889d90dbc7b 100644
--- a/synapse/config/room.py
+++ b/synapse/config/room.py
@@ -1,4 +1,3 @@
-# -*- coding: utf-8 -*-
 # Copyright 2020 The Matrix.org Foundation C.I.C.
 #
 # Licensed under the Apache License, Version 2.0 (the "License");
diff --git a/synapse/config/room_directory.py b/synapse/config/room_directory.py
index 2dd719c388ac..a3cc0b233fcc 100644
--- a/synapse/config/room_directory.py
+++ b/synapse/config/room_directory.py
@@ -1,4 +1,3 @@
-# -*- coding: utf-8 -*-
 # Copyright 2018 New Vector Ltd
 #
 # Licensed under the Apache License, Version 2.0 (the "License");
@@ -170,7 +169,7 @@ def __init__(self, option_name, rule):
             self.action = action
         else:
             raise ConfigError(
-                "%s rules can only have action of 'allow' or 'deny'" % (option_name,)
+                f"{option_name} rules can only have action of 'allow' or 'deny'"
             )
 
         self._alias_matches_all = alias == "*"
diff --git a/synapse/config/saml2_config.py b/synapse/config/saml2_config.py
index 6db9cb5ced3c..c4eb22080699 100644
--- a/synapse/config/saml2_config.py
+++ b/synapse/config/saml2_config.py
@@ -1,4 +1,3 @@
-# -*- coding: utf-8 -*-
 # Copyright 2018 New Vector Ltd
 # Copyright 2019 The Matrix.org Foundation C.I.C.
 #
@@ -317,7 +316,7 @@ def generate_config_section(self, config_dir_path, server_name, **kwargs):
           # Instead of putting the config inline as above, you can specify a
           # separate pysaml2 configuration file:
           #
-          #config_path: "%(config_dir_path)s/sp_conf.py"
+          #config_path: "{config_dir_path}/sp_conf.py"
 
           # The lifetime of a SAML session. This defines how long a user has to
           # complete the authentication process, if allow_unsolicited is unset.
@@ -394,9 +393,9 @@ def generate_config_section(self, config_dir_path, server_name, **kwargs):
           # option.
           #
           #idp_entityid: 'https://our_idp/entityid'
-        """ % {
-            "config_dir_path": config_dir_path
-        }
+        """.format(
+            config_dir_path=config_dir_path
+        )
 
 
 ATTRIBUTE_REQUIREMENTS_SCHEMA = {
diff --git a/synapse/config/server.py b/synapse/config/server.py
index 5f8910b6e149..05b5eb415d37 100644
--- a/synapse/config/server.py
+++ b/synapse/config/server.py
@@ -1,4 +1,3 @@
-# -*- coding: utf-8 -*-
 # Copyright 2014-2016 OpenMarket Ltd
 # Copyright 2017-2018 New Vector Ltd
 # Copyright 2019 The Matrix.org Foundation C.I.C.
@@ -91,9 +90,7 @@ def generate_ip_set(
         try:
             network = IPNetwork(ip)
         except AddrFormatError as e:
-            raise ConfigError(
-                "Invalid IP range provided: %s." % (ip,), config_path
-            ) from e
+            raise ConfigError(f"Invalid IP range provided: {ip}.", config_path) from e
         result.add(network)
 
         # It is possible that these already exist in the set, but that's OK.
diff --git a/synapse/config/server_notices_config.py b/synapse/config/server_notices_config.py
index 57f69dc8e27d..48bf3241b659 100644
--- a/synapse/config/server_notices_config.py
+++ b/synapse/config/server_notices_config.py
@@ -1,4 +1,3 @@
-# -*- coding: utf-8 -*-
 # Copyright 2018 New Vector Ltd
 #
 # Licensed under the Apache License, Version 2.0 (the "License");
diff --git a/synapse/config/spam_checker.py b/synapse/config/spam_checker.py
index 3d05abc1586a..447ba3303b3a 100644
--- a/synapse/config/spam_checker.py
+++ b/synapse/config/spam_checker.py
@@ -1,4 +1,3 @@
-# -*- coding: utf-8 -*-
 # Copyright 2017 New Vector Ltd
 #
 # Licensed under the Apache License, Version 2.0 (the "License");
diff --git a/synapse/config/sso.py b/synapse/config/sso.py
index 243cc681e88d..af645c930d0d 100644
--- a/synapse/config/sso.py
+++ b/synapse/config/sso.py
@@ -1,4 +1,3 @@
-# -*- coding: utf-8 -*-
 # Copyright 2020 The Matrix.org Foundation C.I.C.
 #
 # Licensed under the Apache License, Version 2.0 (the "License");
diff --git a/synapse/config/stats.py b/synapse/config/stats.py
index 2258329a52d8..3d44b5120106 100644
--- a/synapse/config/stats.py
+++ b/synapse/config/stats.py
@@ -1,4 +1,3 @@
-# -*- coding: utf-8 -*-
 # Copyright 2018 New Vector Ltd
 #
 # Licensed under the Apache License, Version 2.0 (the "License");
diff --git a/synapse/config/third_party_event_rules.py b/synapse/config/third_party_event_rules.py
index c04e1c4e077e..f502ff539e27 100644
--- a/synapse/config/third_party_event_rules.py
+++ b/synapse/config/third_party_event_rules.py
@@ -1,4 +1,3 @@
-# -*- coding: utf-8 -*-
 # Copyright 2019 The Matrix.org Foundation C.I.C.
 #
 # Licensed under the Apache License, Version 2.0 (the "License");
diff --git a/synapse/config/tls.py b/synapse/config/tls.py
index ad37b93c0252..9787088b52da 100644
--- a/synapse/config/tls.py
+++ b/synapse/config/tls.py
@@ -1,4 +1,3 @@
-# -*- coding: utf-8 -*-
 # Copyright 2014-2016 OpenMarket Ltd
 #
 # Licensed under the Apache License, Version 2.0 (the "License");
@@ -111,10 +110,8 @@ def read_config(self, config: dict, config_dir_path: str, **kwargs):
         if self.federation_client_minimum_tls_version == "1.3":
             if getattr(SSL, "OP_NO_TLSv1_3", None) is None:
                 raise ConfigError(
-                    (
-                        "federation_client_minimum_tls_version cannot be 1.3, "
-                        "your OpenSSL does not support it"
-                    )
+                    "federation_client_minimum_tls_version cannot be 1.3, "
+                    "your OpenSSL does not support it"
                 )
 
         # Whitelist of domains to not verify certificates for
@@ -164,7 +161,7 @@ def read_config(self, config: dict, config_dir_path: str, **kwargs):
                     certs.append(cert_base)
                 except Exception as e:
                     raise ConfigError(
-                        "Error parsing custom CA certificate file %s: %s" % (ca_file, e)
+                        f"Error parsing custom CA certificate file {ca_file}: {e}"
                     )
 
             self.federation_ca_trust_root = trustRootFromCertificates(certs)
@@ -495,11 +492,9 @@ def read_tls_certificate(self) -> crypto.X509:
         # Check if it is self-signed, and issue a warning if so.
         if cert.get_issuer() == cert.get_subject():
             warnings.warn(
-                (
-                    "Self-signed TLS certificates will not be accepted by Synapse 1.0. "
-                    "Please either provide a valid certificate, or use Synapse's ACME "
-                    "support to provision one."
-                )
+                "Self-signed TLS certificates will not be accepted by Synapse 1.0. "
+                "Please either provide a valid certificate, or use Synapse's ACME "
+                "support to provision one."
             )
 
         return cert
diff --git a/synapse/config/tracer.py b/synapse/config/tracer.py
index 727a1e700838..db22b5b19fb6 100644
--- a/synapse/config/tracer.py
+++ b/synapse/config/tracer.py
@@ -1,4 +1,3 @@
-# -*- coding: utf-8 -*-
 # Copyright 2019 The Matrix.org Foundation C.I.C.d
 #
 # Licensed under the Apache License, Version 2.0 (the "License");
diff --git a/synapse/config/user_directory.py b/synapse/config/user_directory.py
index 8d05ef173c05..4cbf79eeed4c 100644
--- a/synapse/config/user_directory.py
+++ b/synapse/config/user_directory.py
@@ -1,4 +1,3 @@
-# -*- coding: utf-8 -*-
 # Copyright 2017 New Vector Ltd
 #
 # Licensed under the Apache License, Version 2.0 (the "License");
diff --git a/synapse/config/workers.py b/synapse/config/workers.py
index ac92375a85e6..b2540163d1b9 100644
--- a/synapse/config/workers.py
+++ b/synapse/config/workers.py
@@ -1,4 +1,3 @@
-# -*- coding: utf-8 -*-
 # Copyright 2016 OpenMarket Ltd
 #
 # Licensed under the Apache License, Version 2.0 (the "License");