Do no expose pytest-plugin through setuptools, let modules require it when needed

Defining the pytest-plugin though the pytest-plugin [1] makes it loaded by default.
This creates loading issues on modules depending on scheduler but not on
the pytest plugin scheduler exposes as explained in the doc [2]

Instead we'll explicitely define to modules depending on the pytest plugins in
their root conftest [3]:

pytest_plugins = [ "swh.scheduler.pytest_plugin" ]

[1] https://docs.pytest.org/en/stable/writing_plugins.html#setuptools-entry-points

[2] https://docs.pytest.org/en/stable/writing_plugins.html#plugin-discovery-order-at-tool-startup

[3] https://docs.pytest.org/en/stable/writing_plugins.html#requiring-loading-plugins-in-a-test-module-or-conftest-file

Related to D3475
Related to T2484

conftest.py

+# Copyright (C) 2020  The Software Heritage developers
+# See the AUTHORS file at the top-level directory of this distribution
+# License: GNU General Public License version 3, or any later version
+# See top-level LICENSE file for more information
+
+
 from hypothesis import settings
 
 # define tests profile. Full documentation is at:
 # https://hypothesis.readthedocs.io/en/latest/settings.html#settings-profiles
 settings.register_profile("fast", max_examples=5, deadline=5000)
 settings.register_profile("slow", max_examples=20, deadline=5000)
+
+
+pytest_plugins = ["swh.scheduler.pytest_plugin"]

setup.py

@@ -55,8 +55,6 @@ setup(
         swh-scheduler=swh.scheduler.cli:main
         [swh.cli.subcommands]
         scheduler=swh.scheduler.cli:cli
-        [pytest11]
-        pytest_swh_scheduler=swh.scheduler.pytest_plugin
     """,
     classifiers=[
         "Programming Language :: Python :: 3",

swh/scheduler/tests/conftest.py

-# Copyright (C) 2016-2019  The Software Heritage developers
+# Copyright (C) 2016-2020  The Software Heritage developers
 # See the AUTHORS file at the top-level directory of this distribution
 # License: GNU General Public License version 3, or any later version
 # See top-level LICENSE file for more information
@@ -12,10 +12,6 @@ import pytest
 from swh.scheduler.model import ListedOrigin, Lister
 from swh.scheduler.tests.common import LISTERS
 
-from swh.scheduler.pytest_plugin import (  # noqa: F401 (backwards-compat imports)
-    swh_scheduler_celery_app as swh_app,
-    swh_scheduler_celery_worker as celery_session_worker,
-)
 
 # make sure we are not fooled by CELERY_ config environment vars
 for var in [x for x in os.environ.keys() if x.startswith("CELERY")]:

[Phabricator Migration user]

Some references in the commit message have been migrated:

• D3475 is now swh-storage!945 (closed)