debian.tests: Fix test

The scheduler fixture introduced truncates tables in between tests. The debian
tests unfortunately share state and it broke when that changed. This fixes the
test by avoiding the truncation of the scheduler db table "task".

Ideally those tests need to be reworked to avoid sharing state between tests.

[1] https://jenkins.softwareheritage.org/job/DLS/job/tests/1043

swh/lister/debian/tests/conftest.py

@@ -3,13 +3,32 @@
 # License: GNU General Public License version 3, or any later version
 # See top-level LICENSE file for more information
 
+import os
+
 import pytest
 from pytest_postgresql.janitor import DatabaseJanitor
 from sqlalchemy import create_engine
 from sqlalchemy.orm import sessionmaker
 
+from swh.core.db.pytest_plugin import postgresql_fact
 from swh.lister.core.models import SQLBase
+
 from swh.lister.debian import debian_init
+import swh.scheduler
+
+SQL_DIR = os.path.join(os.path.dirname(swh.scheduler.__file__), "sql")
+postgresql_scheduler = postgresql_fact(
+    "postgresql_proc",
+    db_name="scheduler-lister",
+    dump_files=os.path.join(SQL_DIR, "*.sql"),
+    # do not truncate the task tables, it's required in between test
+    no_truncate_tables={"dbversion", "priority_ratio", "task"},
+)
+
+
+@pytest.fixture
+def swh_scheduler_config(postgresql_scheduler):
+    return {"db": postgresql_scheduler.dsn}
 
 
 @pytest.fixture