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/email_mirror.py

@@ -1,31 +1,44 @@
-from typing import Dict, Optional, Tuple, List
-
 import logging
 import re
-
 from email.header import decode_header, make_header
 from email.message import Message as EmailMessage
 from email.utils import getaddresses
+from typing import Dict, List, Optional, Tuple
 
 from django.conf import settings
-from django.utils.timezone import timedelta, now as timezone_now
+from django.utils.timezone import now as timezone_now
+from django.utils.timezone import timedelta
 
-from zerver.lib.actions import internal_send_private_message, \
-    internal_send_stream_message, internal_send_huddle_message
-from zerver.lib.email_mirror_helpers import decode_email_address, \
-    get_email_gateway_message_string_from_address, ZulipEmailForwardError
+from zerver.lib.actions import (
+    internal_send_huddle_message,
+    internal_send_private_message,
+    internal_send_stream_message,
+)
+from zerver.lib.email_mirror_helpers import (
+    ZulipEmailForwardError,
+    decode_email_address,
+    get_email_gateway_message_string_from_address,
+)
 from zerver.lib.email_notifications import convert_html_to_markdown
-from zerver.lib.queue import queue_json_publish
-from zerver.lib.utils import generate_random_token
-from zerver.lib.upload import upload_message_file
-from zerver.lib.send_email import FromAddress
-from zerver.lib.rate_limiter import RateLimitedObject
 from zerver.lib.exceptions import RateLimited
 from zerver.lib.message import truncate_body, truncate_topic
-from zerver.models import Stream, Recipient, MissedMessageEmailAddress, \
-    get_display_recipient, \
-    Message, Realm, UserProfile, get_system_bot, get_user, get_stream_by_id_in_realm
-
+from zerver.lib.queue import queue_json_publish
+from zerver.lib.rate_limiter import RateLimitedObject
+from zerver.lib.send_email import FromAddress
+from zerver.lib.upload import upload_message_file
+from zerver.lib.utils import generate_random_token
+from zerver.models import (
+    Message,
+    MissedMessageEmailAddress,
+    Realm,
+    Recipient,
+    Stream,
+    UserProfile,
+    get_display_recipient,
+    get_stream_by_id_in_realm,
+    get_system_bot,
+    get_user,
+)
 from zproject.backends import is_user_active
 
 logger = logging.getLogger(__name__)