python: Sort imports with isort.

Fixes #2665.

Regenerated by tabbott with `lint --fix` after a rebase and change in
parameters.

Note from tabbott: In a few cases, this converts technical debt in the
form of unsorted imports into different technical debt in the form of
our largest files having very long, ugly import sequences at the
start.  I expect this change will increase pressure for us to split
those files, which isn't a bad thing.

Signed-off-by: Anders Kaseorg <anders@zulip.com>

zerver/lib/cache_helpers.py

@@ -1,28 +1,38 @@
 # See https://zulip.readthedocs.io/en/latest/subsystems/caching.html for docs
-
-from typing import Any, Callable, Dict, List, Tuple
-
 import datetime
 import logging
+from importlib import import_module
+from typing import Any, Callable, Dict, List, Tuple
+
+from django.conf import settings
+from django.contrib.sessions.models import Session
+from django.db.models import Q
+from django.utils.timezone import now as timezone_now
 
 # This file needs to be different from cache.py because cache.py
 # cannot import anything from zerver.models or we'd have an import
 # loop
 from analytics.models import RealmCount
-from django.conf import settings
-from zerver.models import Message, UserProfile, Stream, get_stream_cache_key, \
-    Client, get_client_cache_key, \
-    Huddle, huddle_hash_cache_key
-from zerver.lib.cache import \
-    user_profile_by_api_key_cache_key, \
-    user_profile_cache_key, get_remote_cache_time, get_remote_cache_requests, \
-    cache_set_many, to_dict_cache_key_id
+from zerver.lib.cache import (
+    cache_set_many,
+    get_remote_cache_requests,
+    get_remote_cache_time,
+    to_dict_cache_key_id,
+    user_profile_by_api_key_cache_key,
+    user_profile_cache_key,
+)
 from zerver.lib.message import MessageDict
 from zerver.lib.users import get_all_api_keys
-from importlib import import_module
-from django.contrib.sessions.models import Session
-from django.db.models import Q
-from django.utils.timezone import now as timezone_now
+from zerver.models import (
+    Client,
+    Huddle,
+    Message,
+    Stream,
+    UserProfile,
+    get_client_cache_key,
+    get_stream_cache_key,
+    huddle_hash_cache_key,
+)
 
 MESSAGE_CACHE_SIZE = 75000