isort 5 compatibility (#7786)

The CI appears to use the latest version of isort, which is a problem when isort gets a major version bump. Rather than try to pin the version, I've done the necessary to make isort5 happy with synapse.

synapse/replication/tcp/client.py

@@ -33,8 +33,8 @@ from synapse.util.async_helpers import timeout_deferred
 from synapse.util.metrics import Measure
 
 if TYPE_CHECKING:
-    from synapse.server import HomeServer
     from synapse.replication.tcp.handler import ReplicationCommandHandler
+    from synapse.server import HomeServer
 
 logger = logging.getLogger(__name__)
 

synapse/replication/tcp/handler.py

@@ -13,7 +13,6 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
-
 import logging
 from typing import Any, Dict, Iterable, Iterator, List, Optional, Set, Tuple, TypeVar
 
@@ -149,10 +148,11 @@ class ReplicationCommandHandler:
         using TCP.
         """
         if hs.config.redis.redis_enabled:
+            import txredisapi
+
             from synapse.replication.tcp.redis import (
                 RedisDirectTcpReplicationClientFactory,
             )
-            import txredisapi
 
             logger.info(
                 "Connecting to redis (host=%r port=%r)",

synapse/replication/tcp/streams/events.py

@@ -13,7 +13,6 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
-
 import heapq
 from collections import Iterable
 from typing import List, Tuple, Type
@@ -22,7 +21,6 @@ import attr
 
 from ._base import Stream, StreamUpdateResult, Token, current_token_without_instance
 
-
 """Handling of the 'events' replication stream
 
 This stream contains rows of various types. Each row therefore contains a 'type'