move initialize_database_for_module in db_utils

to prepare the deprecation of db/pytest_plugin.py; it's the only
function from db/pytest_plugin.py still in use.

swh/core/db/db_utils.py

@@ -548,6 +548,33 @@ def populate_database_for_package(
     return True, current_db_version, dbflavor
 
 
+def initialize_database_for_module(modname: str, version: int, **kwargs):
+    """Helper function to initialize and populate a database for the given module
+
+    This aims at helping the usage of pytest_postgresql for swh.core.db based datastores.
+    Typical usage will be (here for swh.storage)::
+
+      from pytest_postgresql import factories
+
+      storage_postgresql_proc = factories.postgresql_proc(
+        load=[partial(initialize_database_for_module, modname="storage", version=42)]
+      )
+      storage_postgresql = factories.postgresql("storage_postgresql_proc")
+
+    """
+    conninfo = psycopg2.connect(**kwargs).dsn
+    init_admin_extensions(modname, conninfo)
+    populate_database_for_package(modname, conninfo)
+    try:
+        swh_set_db_version(conninfo, version)
+    except psycopg2.errors.UniqueViolation:
+        logger.warn(
+            "Version already set by db init scripts. "
+            f"This generally means the swh.{modname} package needs to be "
+            "updated for swh.core>=1.2"
+        )
+
+
 def get_database_info(
     conninfo: str,
 ) -> Tuple[Optional[str], Optional[int], Optional[str]]:

swh/core/db/pytest_plugin.py

@@ -18,11 +18,7 @@ from pytest_postgresql.executor import PostgreSQLExecutor
 from pytest_postgresql.executor_noop import NoopExecutor
 from pytest_postgresql.janitor import DatabaseJanitor
 
-from swh.core.db.db_utils import (
-    init_admin_extensions,
-    populate_database_for_package,
-    swh_set_db_version,
-)
+from swh.core.db.db_utils import initialize_database_for_module
 from swh.core.utils import basename_sortkey
 
 # to keep mypy happy regardless pytest-postgresql version
@@ -37,6 +33,11 @@ _pytest_postgresql_get_config = getattr(_pytest_pgsql_get_config_module, "get_co
 
 logger = logging.getLogger(__name__)
 
+initialize_database_for_module = deprecated(
+    version="2.10",
+    reason="Use swh.core.db.db_utils.initialize_database_for_module instead.",
+)(initialize_database_for_module)
+
 
 class SWHDatabaseJanitor(DatabaseJanitor):
     """SWH database janitor implementation with a a different setup/teardown policy than
@@ -254,20 +255,6 @@ def postgresql_fact(
     return postgresql_factory
 
 
-def initialize_database_for_module(modname, version, **kwargs):
-    conninfo = psycopg2.connect(**kwargs).dsn
-    init_admin_extensions(modname, conninfo)
-    populate_database_for_package(modname, conninfo)
-    try:
-        swh_set_db_version(conninfo, version)
-    except psycopg2.errors.UniqueViolation:
-        logger.warn(
-            "Version already set by db init scripts. "
-            "This generally means the swh.{modname} package needs to be "
-            "updated for swh.core>=1.2"
-        )
-
-
 def gen_dump_files(dump_files: Union[str, Iterable[str]]) -> Iterator[str]:
     """Generate files potentially resolving glob patterns if any"""
     if isinstance(dump_files, str):