Fix tox for Python >= 3.12

Fix import error:
```
py312-cov: commands[2]> pytest --cov --cov-report=xml --cov-report=html --cov-report=term --tb=short
ImportError while loading conftest '/home/rominf/dev/aiosmtpd/aiosmtpd/tests/conftest.py'.
aiosmtpd/tests/conftest.py:15: in <module>
    from pkg_resources import resource_filename
E   ModuleNotFoundError: No module named 'pkg_resources'
```
by migrating to `importlib.resources`.

Author: rominf

aiosmtpd/tests/conftest.py

@@ -2,17 +2,19 @@
 # SPDX-License-Identifier: Apache-2.0
 
 import asyncio
+import importlib.resources
 import inspect
 import socket
 import ssl
+import sys
 import warnings
 from contextlib import suppress
 from functools import wraps
+from pathlib import Path
 from smtplib import SMTP as SMTPClient
 from typing import Any, Callable, Generator, NamedTuple, Optional, Type, TypeVar
 
 import pytest
-from pkg_resources import resource_filename
 from pytest_mock import MockFixture
 
 from aiosmtpd.controller import Controller
@@ -32,8 +34,6 @@
     "handler_data",
     "Global",
     "AUTOSTOP_DELAY",
-    "SERVER_CRT",
-    "SERVER_KEY",
 ]
 
 
@@ -73,8 +73,6 @@ def set_addr_from(cls, contr: Controller):
 # If less than 1.0, might cause intermittent error if test system
 # is too busy/overloaded.
 AUTOSTOP_DELAY = 1.5
-SERVER_CRT = resource_filename("aiosmtpd.tests.certs", "server.crt")
-SERVER_KEY = resource_filename("aiosmtpd.tests.certs", "server.key")
 
 # endregion
 
@@ -99,6 +97,22 @@ def cache_fqdn(session_mocker: MockFixture):
 # region #### Common Fixtures #########################################################
 
 
+def _server_resource(name: str, /) -> Generator[Path, None, None]:
+    ref = importlib.resources.files("aiosmtpd.tests.certs") / name
+    with importlib.resources.as_file(ref) as path:
+        yield path
+
+
+@pytest.fixture(scope="session")
+def server_crt() -> Generator[Path, None, None]:
+    yield from _server_resource("server.crt")
+
+
+@pytest.fixture(scope="session")
+def server_key() -> Generator[Path, None, None]:
+    yield from _server_resource("server.key")
+
+
 @pytest.fixture
 def get_controller(request: pytest.FixtureRequest) -> Callable[..., Controller]:
     """
@@ -315,25 +329,25 @@ def client(request: pytest.FixtureRequest) -> Generator[SMTPClient, None, None]:
 
 
 @pytest.fixture
-def ssl_context_server() -> ssl.SSLContext:
+def ssl_context_server(server_crt: Path, server_key: Path) -> ssl.SSLContext:
     """
     Provides a server-side SSL Context
     """
     context = ssl.create_default_context(ssl.Purpose.CLIENT_AUTH)
     context.check_hostname = False
-    context.load_cert_chain(SERVER_CRT, SERVER_KEY)
+    context.load_cert_chain(server_crt, server_key)
     #
     return context
 
 
 @pytest.fixture
-def ssl_context_client() -> ssl.SSLContext:
+def ssl_context_client(server_crt: Path) -> ssl.SSLContext:
     """
     Provides a client-side SSL Context
     """
     context = ssl.create_default_context(ssl.Purpose.SERVER_AUTH)
     context.check_hostname = False
-    context.load_verify_locations(SERVER_CRT)
+    context.load_verify_locations(server_crt)
     #
     return context
 

aiosmtpd/tests/test_main.py

@@ -9,6 +9,7 @@
 import time
 from contextlib import contextmanager
 from multiprocessing.synchronize import Event as MP_Event
+from pathlib import Path
 from smtplib import SMTP as SMTPClient
 from smtplib import SMTP_SSL
 from typing import Generator
@@ -21,7 +22,7 @@
 from aiosmtpd.main import main, parseargs
 from aiosmtpd.testing.helpers import catchup_delay
 from aiosmtpd.testing.statuscodes import SMTP_STATUS_CODES as S
-from aiosmtpd.tests.conftest import AUTOSTOP_DELAY, SERVER_CRT, SERVER_KEY
+from aiosmtpd.tests.conftest import AUTOSTOP_DELAY
 
 try:
     import pwd
@@ -199,24 +200,24 @@ def test_debug_3(self):
 
 @pytest.mark.skipif(sys.platform == "darwin", reason="No idea why these are failing")
 class TestMainByWatcher:
-    def test_tls(self, temp_event_loop):
+    def test_tls(self, temp_event_loop, server_crt: Path, server_key: Path):
         with watcher_process(watch_for_tls) as retq:
             temp_event_loop.call_later(AUTOSTOP_DELAY, temp_event_loop.stop)
-            main_n("--tlscert", str(SERVER_CRT), "--tlskey", str(SERVER_KEY))
+            main_n("--tlscert", str(server_crt), "--tlskey", str(server_key))
             catchup_delay()
         has_starttls = retq.get()
         assert has_starttls is True
         require_tls = retq.get()
         assert require_tls is True
 
-    def test_tls_noreq(self, temp_event_loop):
+    def test_tls_noreq(self, temp_event_loop, server_crt: Path, server_key: Path):
         with watcher_process(watch_for_tls) as retq:
             temp_event_loop.call_later(AUTOSTOP_DELAY, temp_event_loop.stop)
             main_n(
                 "--tlscert",
-                str(SERVER_CRT),
+                str(server_crt),
                 "--tlskey",
-                str(SERVER_KEY),
+                str(server_key),
                 "--no-requiretls",
             )
             catchup_delay()
@@ -225,10 +226,10 @@ def test_tls_noreq(self, temp_event_loop):
         require_tls = retq.get()
         assert require_tls is False
 
-    def test_smtps(self, temp_event_loop):
+    def test_smtps(self, temp_event_loop, server_crt: Path, server_key: Path):
         with watcher_process(watch_for_smtps) as retq:
             temp_event_loop.call_later(AUTOSTOP_DELAY, temp_event_loop.stop)
-            main_n("--smtpscert", str(SERVER_CRT), "--smtpskey", str(SERVER_KEY))
+            main_n("--smtpscert", str(server_crt), "--smtpskey", str(server_key))
             catchup_delay()
         has_smtps = retq.get()
         assert has_smtps is True
@@ -335,19 +336,21 @@ def test_norequiretls(self, capsys, mocker):
         assert args.requiretls is False
 
     @pytest.mark.parametrize(
-        ("certfile", "keyfile", "expect"),
+        ("certfile_present", "keyfile_present", "expect"),
         [
-            ("x", "x", "Cert file x not found"),
-            (SERVER_CRT, "x", "Key file x not found"),
-            ("x", SERVER_KEY, "Cert file x not found"),
+            (False, False, "Cert file x not found"),
+            (True, False, "Key file x not found"),
+            (False, True, "Cert file x not found"),
         ],
         ids=["x-x", "cert-x", "x-key"],
     )
     @pytest.mark.parametrize("meth", ["smtps", "tls"])
-    def test_ssl_files_err(self, capsys, mocker, meth, certfile, keyfile, expect):
+    def test_ssl_files_err(self, capsys, mocker, meth, certfile_present, keyfile_present, expect, request: pytest.FixtureRequest):
+        certfile = request.getfixturevalue("server_crt") if certfile_present else "x"
+        keyfile = request.getfixturevalue("server_key") if keyfile_present else "x"
         mocker.patch("aiosmtpd.main.PROGRAM", "smtpd")
         with pytest.raises(SystemExit) as exc:
-            parseargs((f"--{meth}cert", certfile, f"--{meth}key", keyfile))
+            parseargs((f"--{meth}cert", str(certfile), f"--{meth}key", str(keyfile)))
         assert exc.value.code == 2
         assert expect in capsys.readouterr().err
 

pytest.ini

@@ -13,8 +13,6 @@ addopts =
 asyncio_mode = auto
 filterwarnings =
     error
-    # TODO: Replace pkg_resources
-    ignore:pkg_resources is deprecated as an API:DeprecationWarning
     # TODO: Fix resource warnings
     ignore:unclosed transport:ResourceWarning
     ignore:unclosed <socket.socket:ResourceWarning