Rework skipping long tests

The ability to conveniently mark tests which should only be run when the
CI_ENABLE_ALL_TESTS environment variable is set seems to be useful on a
general level and therefore it should not be limited to the "timeouts"
system test, where it is currently used.

pytest documentation [1] suggests to reuse commonly used test markers by
putting them all in a single Python module which then has to be imported
by test files that want to use the markers defined therein.  Follow that
advice by creating a new bin/tests/system/pytest_custom_markers.py
Python module containing the relevant marker definitions.

Note that "import pytest_custom_markers" works from a test-specific
subdirectory because pytest modifies sys.path so that it contains the
paths to all parent directories containing a conftest.py file (and
bin/tests/system/ is one).  PyLint does not like that, though, so add a
relevant PyLint suppression.

The above changes make bin/tests/system/timeouts/conftest.py redundant,
so remove it.

[1] https://docs.pytest.org/en/7.0.x/how-to/skipping.html#id1

bin/tests/system/pytest_custom_markers.py

@@ -0,0 +1,20 @@
+#!/usr/bin/python3
+
+# Copyright (C) Internet Systems Consortium, Inc. ("ISC")
+#
+# SPDX-License-Identifier: MPL-2.0
+#
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0.  If a copy of the MPL was not distributed with this
+# file, you can obtain one at https://mozilla.org/MPL/2.0/.
+#
+# See the COPYRIGHT file distributed with this work for additional
+# information regarding copyright ownership.
+
+import os
+
+import pytest
+
+
+long_test = pytest.mark.skipif(not os.environ.get('CI_ENABLE_ALL_TESTS'),
+                               reason='CI_ENABLE_ALL_TESTS not set')

bin/tests/system/run.sh.in

@@ -111,7 +111,7 @@ if [ "${srcdir}" != "${builddir}" ]; then
         cp -a "${srcdir}/common" "${builddir}"
     fi
     # Some tests require additional files to work for out-of-tree test runs.
-    for file in ckdnsrps.sh conftest.py digcomp.pl ditch.pl fromhex.pl kasp.sh packet.pl start.pl stop.pl testcrypto.sh; do
+    for file in ckdnsrps.sh conftest.py digcomp.pl ditch.pl fromhex.pl kasp.sh packet.pl pytest_custom_markers.py start.pl stop.pl testcrypto.sh; do
         if [ ! -r "${file}" ]; then
             cp -a "${srcdir}/${file}" "${builddir}"
         fi

bin/tests/system/timeouts/conftest.py

@@ -1,30 +0,0 @@
-# Copyright (C) Internet Systems Consortium, Inc. ("ISC")
-#
-# SPDX-License-Identifier: MPL-2.0
-#
-# This Source Code Form is subject to the terms of the Mozilla Public
-# License, v. 2.0.  If a copy of the MPL was not distributed with this
-# file, you can obtain one at https://mozilla.org/MPL/2.0/.
-#
-# See the COPYRIGHT file distributed with this work for additional
-# information regarding copyright ownership.
-
-import os
-import pytest
-
-
-def pytest_configure(config):
-    config.addinivalue_line(
-        "markers", "long: mark tests that take a long time to run"
-    )
-
-
-def pytest_collection_modifyitems(config, items):
-    # pylint: disable=unused-argument,unused-import,too-many-branches
-    # pylint: disable=import-outside-toplevel
-    skip_long_tests = pytest.mark.skip(
-        reason="need CI_ENABLE_ALL_TESTS environment variable")
-    if not os.environ.get("CI_ENABLE_ALL_TESTS"):
-        for item in items:
-            if "long" in item.keywords:
-                item.add_marker(skip_long_tests)

bin/tests/system/timeouts/tests-tcp.py

@@ -26,6 +26,8 @@ import dns.query
 import dns.rdataclass
 import dns.rdatatype
 
+import pytest_custom_markers  # pylint: disable=import-error
+
 
 TIMEOUT = 10
 
@@ -204,7 +206,7 @@ def test_send_timeout(named_port):
                 raise EOFError from e
 
 
-@pytest.mark.long
+@pytest_custom_markers.long_test
 def test_max_transfer_idle_out(named_port):
     with socket.socket(socket.AF_INET, socket.SOCK_STREAM) as sock:
         sock.connect(("10.53.0.1", named_port))
@@ -235,7 +237,7 @@ def test_max_transfer_idle_out(named_port):
             assert soa is None
 
 
-@pytest.mark.long
+@pytest_custom_markers.long_test
 def test_max_transfer_time_out(named_port):
     with socket.socket(socket.AF_INET, socket.SOCK_STREAM) as sock:
         sock.connect(("10.53.0.1", named_port))