[db] Always run PRAGMA foreign_keys = ON on SQLite connections.

This is the default behaviour on basically any other supported RDBMS.

platypush/plugins/db/__init__.py

@@ -533,13 +533,19 @@ class DbPlugin(Plugin):
         with lock, engine.connect() as conn:
             session_maker = scoped_session(
                 sessionmaker(
-                    expire_on_commit=False,
+                    expire_on_commit=kwargs.get('expire_on_commit', False),
                     autoflush=autoflush,
                 )
             )
 
             session_maker.configure(bind=conn)
             session = session_maker()
+
+            if str(session.connection().engine.url).startswith('sqlite://'):
+                # SQLite requires foreign_keys to be explicitly enabled
+                # in order to proper manage cascade deletions
+                session.execute(text('PRAGMA foreign_keys = ON'))
+
             yield session
 
             session.flush()

platypush/plugins/entities/__init__.py

@@ -4,7 +4,7 @@ from time import time
 from traceback import format_exception
 from typing import Optional, Any, Collection, Mapping
 
-from sqlalchemy import or_, text
+from sqlalchemy import or_
 from sqlalchemy.orm import make_transient, Session
 
 from platypush.config import Config
@@ -206,11 +206,6 @@ class EntitiesPlugin(Plugin):
         :return: The payload of the deleted entities.
         """
         with self._get_session(locked=True) as session:
-            if str(session.connection().engine.url).startswith('sqlite://'):
-                # SQLite requires foreign_keys to be explicitly enabled
-                # in order to proper manage cascade deletions
-                session.execute(text('PRAGMA foreign_keys = ON'))
-
             entities: Collection[Entity] = (
                 session.query(Entity).filter(Entity.id.in_(entities)).all()
             )