Remove 3.6 compatibility shims

- asyncio.all_tasks/current_task
- pytest-asyncio 0.17
- contextmanager.nullcontext

dev-requirements.txt

@@ -16,8 +16,7 @@ mock
 nbclassic<0.4
 pre-commit
 pytest>=3.3
-pytest-asyncio; python_version < "3.7"
-pytest-asyncio>=0.17; python_version >= "3.7"
+pytest-asyncio>=0.17
 pytest-cov
 requests-mock
 tbump

jupyterhub/app.py

@@ -23,15 +23,6 @@ from urllib.parse import unquote, urlparse, urlunparse
 if sys.version_info[:2] < (3, 3):
     raise ValueError("Python < 3.3 not supported: %s" % sys.version)
 
-# For compatibility with python versions 3.6 or earlier.
-# asyncio.Task.all_tasks() is fully moved to asyncio.all_tasks() starting with 3.9. Also applies to current_task.
-try:
-    asyncio_all_tasks = asyncio.all_tasks
-    asyncio_current_task = asyncio.current_task
-except AttributeError as e:
-    asyncio_all_tasks = asyncio.Task.all_tasks
-    asyncio_current_task = asyncio.Task.current_task
-
 import tornado.httpserver
 import tornado.options
 from dateutil.parser import parse as parse_date
@@ -3248,7 +3239,7 @@ class JupyterHub(Application):
 
         await self.cleanup()
 
-        tasks = [t for t in asyncio_all_tasks() if t is not asyncio_current_task()]
+        tasks = [t for t in asyncio.all_tasks() if t is not asyncio.current_task()]
 
         if tasks:
             self.log.debug("Cancelling pending tasks")
@@ -3261,7 +3252,7 @@ class JupyterHub(Application):
             except StopAsyncIteration as e:
                 self.log.error("Caught StopAsyncIteration Exception", exc_info=True)
 
-            tasks = [t for t in asyncio_all_tasks()]
+            tasks = [t for t in asyncio.all_tasks()]
             for t in tasks:
                 self.log.debug("Task status: %s", t)
         asyncio.get_event_loop().stop()

jupyterhub/tests/conftest.py

@@ -54,28 +54,6 @@ from .utils import add_user
 _db = None
 
 
-def _pytest_collection_modifyitems(items):
-    """This function is automatically run by pytest passing all collected test
-    functions.
-
-    We use it to add asyncio marker to all async tests and assert we don't use
-    test functions that are async generators which wouldn't make sense.
-
-    It is no longer required with pytest-asyncio >= 0.17
-    """
-    for item in items:
-        if inspect.iscoroutinefunction(item.obj):
-            item.add_marker('asyncio')
-        assert not inspect.isasyncgenfunction(item.obj)
-
-
-if sys.version_info < (3, 7):
-    # apply pytest-asyncio's 'auto' mode on Python 3.6.
-    # 'auto' mode is new in pytest-asyncio 0.17,
-    # which requires Python 3.7.
-    pytest_collection_modifyitems = _pytest_collection_modifyitems
-
-
 @fixture(scope='module')
 def ssl_tmpdir(tmpdir_factory):
     return tmpdir_factory.mktemp('ssl')

jupyterhub/tests/test_singleuser.py

@@ -1,7 +1,7 @@
 """Tests for jupyterhub.singleuser"""
 import os
 import sys
-from contextlib import contextmanager
+from contextlib import contextmanager, nullcontext
 from subprocess import CalledProcessError, check_output
 from unittest import mock
 from urllib.parse import urlencode, urlparse
@@ -17,12 +17,6 @@ from .mocking import StubSingleUserSpawner, public_url
 from .utils import AsyncSession, async_requests, get_page
 
 
-@contextmanager
-def nullcontext():
-    """Python 3.7+ contextlib.nullcontext, backport for 3.6"""
-    yield
-
-
 @pytest.mark.parametrize(
     "access_scopes, server_name, expect_success",
     [

jupyterhub/utils.py

@@ -27,14 +27,26 @@ from tornado import gen, ioloop, web
 from tornado.httpclient import AsyncHTTPClient, HTTPError
 from tornado.log import app_log
 
-# For compatibility with python versions 3.6 or earlier.
-# asyncio.Task.all_tasks() is fully moved to asyncio.all_tasks() starting with 3.9. Also applies to current_task.
-try:
-    asyncio_all_tasks = asyncio.all_tasks
-    asyncio_current_task = asyncio.current_task
-except AttributeError as e:
-    asyncio_all_tasks = asyncio.Task.all_tasks
-    asyncio_current_task = asyncio.Task.current_task
+
+# Deprecated aliases: no longer needed now that we require 3.7
+def asyncio_all_tasks(loop=None):
+    warnings.warn(
+        "jupyterhub.utils.asyncio_all_tasks is deprecated in JupyterHub 2.4."
+        " Use asyncio.all_tasks().",
+        DeprecationWarning,
+        stacklevel=2,
+    )
+    return asyncio.all_tasks(loop=loop)
+
+
+def asyncio_current_task(loop=None):
+    warnings.warn(
+        "jupyterhub.utils.asyncio_current_task is deprecated in JupyterHub 2.4."
+        " Use asyncio.current_task().",
+        DeprecationWarning,
+        stacklevel=2,
+    )
+    return asyncio.current_task(loop=loop)
 
 
 def random_port():