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/views/documentation.py

@@ -1,22 +1,22 @@
-from typing import Any, Dict, Tuple
-from collections import OrderedDict
-from django.views.generic import TemplateView
-from django.conf import settings
-from django.http import HttpRequest, HttpResponse, HttpResponseNotFound
-from django.template import loader
-
 import os
 import random
 import re
+from collections import OrderedDict
+from typing import Any, Dict, Tuple
 
+from django.conf import settings
+from django.http import HttpRequest, HttpResponse, HttpResponseNotFound
+from django.template import loader
+from django.views.generic import TemplateView
+
+from zerver.context_processors import zulip_default_context
 from zerver.decorator import add_google_analytics_context
-from zerver.lib.integrations import CATEGORIES, INTEGRATIONS, HubotIntegration, \
-    WebhookIntegration
-from zerver.lib.request import has_request_variables, REQ
+from zerver.lib.integrations import CATEGORIES, INTEGRATIONS, HubotIntegration, WebhookIntegration
+from zerver.lib.request import REQ, has_request_variables
 from zerver.lib.subdomains import get_subdomain
 from zerver.models import Realm
 from zerver.templatetags.app_filters import render_markdown_path
-from zerver.context_processors import zulip_default_context
+
 
 def add_api_uri_context(context: Dict[str, Any], request: HttpRequest) -> None:
     context.update(zulip_default_context(request))