python: Use standard NoReturn (Python ≥ 3.6).

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

puppet/zulip/files/nagios_plugins/zulip_nagios_server/check_postgres_replication_lag

@@ -8,11 +8,7 @@ secondary Postgres servers' xlog location.
 import configparser
 import subprocess
 import re
-
-from typing import TYPE_CHECKING
-if TYPE_CHECKING:
-    # typing_extensions might not be installed
-    from typing_extensions import NoReturn
+from typing import NoReturn
 
 states = {
     "OK": 0,

requirements/common.in

@@ -5,7 +5,7 @@
 # Django itself
 Django==2.2.*
 
-# needed for Deque (in Python < 3.5.4) and TypedDict
+# needed for Literal, TypedDict
 typing-extensions
 
 # Needed for rendering backend templates

tools/lib/provision.py

@@ -24,8 +24,7 @@ from tools.setup import setup_venvs
 
 from typing import List, TYPE_CHECKING
 if TYPE_CHECKING:
-    # typing_extensions might not be installed yet
-    from typing_extensions import NoReturn
+    from typing import NoReturn
 
 VAR_DIR_PATH = os.path.join(ZULIP_PATH, 'var')
 

tools/webpack

@@ -4,7 +4,7 @@ import argparse
 import os
 import json
 import subprocess
-from typing_extensions import NoReturn
+from typing import NoReturn
 
 os.chdir(os.path.join(os.path.dirname(__file__), '..'))
 STATIC_PATH = 'static/'

zerver/lib/exceptions.py

@@ -1,6 +1,5 @@
 from enum import Enum
-from typing import Any, Dict, List, Type, TypeVar, Optional
-from typing_extensions import NoReturn
+from typing import Any, Dict, List, NoReturn, Type, TypeVar, Optional
 
 from django.utils.translation import ugettext as _
 

zerver/tests/test_logging_handlers.py

@@ -9,8 +9,7 @@ from django.utils.log import AdminEmailHandler
 from functools import wraps
 from unittest.mock import MagicMock, patch
 from types import TracebackType
-from typing import Any, Callable, Dict, Iterator, Optional, Tuple, Type
-from typing_extensions import NoReturn
+from typing import Any, Callable, Dict, Iterator, NoReturn, Optional, Tuple, Type
 
 from zerver.lib.types import ViewFuncT
 from zerver.lib.test_classes import ZulipTestCase

zerver/tornado/event_queue.py

@@ -1,8 +1,8 @@
 # See https://zulip.readthedocs.io/en/latest/subsystems/events-system.html for
 # high-level documentation on how this system works.
-from typing import cast, AbstractSet, Any, Callable, Dict, List, \
+from typing import cast, AbstractSet, Any, Callable, Deque, Dict, List, \
     Mapping, MutableMapping, Optional, Iterable, Sequence, Set, Union
-from typing_extensions import Deque, TypedDict
+from typing_extensions import TypedDict
 
 from django.utils.translation import ugettext as _
 from django.conf import settings